(GIFT   OF 
MICHAEL  REESE 


1Rav>al  Hvcbitecture : 

A 

Manual  on  Laying-off 

IRON,  STEEL,  AND  COMPOSITE  VESSELS. 

BY 

THOMAS  H.  WATSON, 

Lecturer  on  Naval  Architecture  at  the  Durham  College  of  Science, 

Newcastle-upon-Tyne  ; 

Member  of  the  North  East  Coast  Institution  of 
Engineers  and  Shipbuilders. 


With   Numerous  Illustrations. 

t^        OF  THE  ' 

UNIVERSITY 
cauforh^ 

London:  Longmans,  Green,  &  Co.,  39,  Paternoster  Row, 
New  York  and  Bombay. 

Newcastle-upon-Tyne  :  Andrew  Reid  &  Company,  Limited. 

189S. 
All  Rights  Reserved.]  [Entered  at  Stationers''  Hall. 


A 


^ :  & 


London  and  Newcastle-upon-Tyne  : 
Andrew  Retd  &  Company,  Limited,  Printers  and  Pi  blushers 


76  2.  2_/ 


Copyright. 


PREFACE.  z™™ 


»£LcaliforH\L 


-*+*- 


This  Manual  has  been  written  to  meet  a  need  amongst 
junior  ship-draughtsmen,  apprentice  loftsmen,  and  class 
students.  The  Author  trusts  it  may  answer  its  purpose,  for 
he  has  sought  to  make  the  subject  clear  by  graphic  sketch 
and  everyday  shipyard  language. 

After  careful  consideration,  it  was  thought  it  would  be 
almost  a  repetition  to  enter  very  fully  into  the  laying-off  of 
Avar  vessels  on  the  loft  floor;  attention,  however,  has  been 
given  to  explaining  some  of  the  more  prominent  parts  which 
distinguish  this  class  of  work. 

The  Author  has  to  express  his  obligations  to  the  loftsmen 
of  the  yards  where  he  has  had  the  pleasure  of  being  located 
at  different  times,  whom  he  has  found,  without  exception, 
always  willing  to  show  the  points  of  their  craft.  Especial 
thanks  are  due  to  the  firm  of  Messrs.  William  Doxford  &  Sons, 
Sunderland,  for  early  instruction  in  practical  laying-off. 

The  Author  wishes  to  express  his  gratitude  to  the  following 
firms,  who  have  willingly  helped  in  this  work  by  giving  access 
to  drawings  of  special  parts : — 

Messrs.  Swan  &  Hunter,  Limited,  Wallsend-upon-Tyne. 

Messrs.  Palmer's  Iron  and  Engineering-  Works,  Jarrow- 
upon-Tyne. 

Messrs.  Wigham  Richardson  &  Co.,  Walker-upon-Tyne. 

Colonel  H.  F.  Swan,  J. P.,  of  Messrs.  Armstrong,  Whit- 
worth,  &  Co.,  Walker-upon-Tyne. 

He  is  further  under  obligation  to  the  late  Professor 
Rankine's  most  excellent  and  advanced  work,  Shipbuilding, 
Theoretical  and  Practical. 

Any  suggestions  tending  to  make  the  book  more  perfect 
for  future  editions,  will  be  gladly  received  by  the  Author, 

Thomas  H.  Watson. 

0 

Newcastle-upon-Tyne, 
January,   1898. 


CONTENTS 


MERCANTILE    VESSELS. 

Chapter  I.— Laying-off  the  Sheer  Draught  on  the 
Loft  Floor. 

Explanation  of  the  Sheer  Draught— Profile,  Half  Breadth  and  Body 
Plans— Lines  Composing  these  Plans— How  they  appear  in  the 
Sheer  Draught — True  Form  of  the  Lines— Particulars  given  to 
Lay  Ship  Down — Midship  Section — Explanation  of  Terms— Length 
over  all — Length  between  Perpendiculars — Moulded  Beam  — 
Moulded  Depth — Rise  of  Bottom—  Tumble-home—  Deadflat—  Turn 
of  Bilge — Camber  of  Beam —Fore-foot — Depth  of  Hold — Change  of 
Frames — Classification  Length  and  Depth — Flam — Laying-off  the 
Vessel  on  the  Loft  Floor — Mode  of  Procedure — Drawing  in  the 
Profile,  Body,  and  Half  Breadth  Plans  — Fairing-up  the  Body  Plan 
— The  Best  Lines  for  Fairing-up  —Projection  of  Bilge  Diagonal — 
Definition  of  Fairness — Definition  of  Fair  Line— Use  of  Diagonals — 
Raised  Keel — Final  Test  of  Fairness — Fairing  by  Contraction — 
Definition  of  a  Bow  Line  and  Buttock — Definition  of  a  Bilge 
Diagonal — Twin  Screw  Bossing— Twin  Screw  Bossing,  Covered 
Shaft— Bossed  Frames  Aft— Finish  of  the  After  End— Fairing-up 
the  Stern — Diagonal  Line  Cutting  Knuckle — To  Fair  Frames  from 
the  Transom  by  a  Diagonal— To  Fair  Frames  from  the  Knuckle  by 
a  Diagonal  —  Sheer  Line — Approximate  Sheer— Construction  of  a 
Sheer  Idagram — Another  Method  of  Constructing  Sheer  Diagram — 
Lowest  Point  of  Sheer  -  Ready  Method  of  Finding  Sheer  Line — 
Sheer  under  Freeboard  Tables — Messrs.  Swan  &  Hunter's  Method 
of  Laying-off    ...         ...         ...         ...         ...         ...  ...  ...    pp.     1 — 26 

Chapter  II. — Cant  Frames. 

Cant  Frames  in  the  Fore  Body— Projection  into  the  Sheer — True  Form 
in  the  Sheer — Projection  into  the  Body  — Projection  into  the  Sheer 
on  Diagonal  Lines — Expansion  of  the  Moulded  Edge  in  the  Sheer 
on  Diagonal  Lines — Expansion  of  the  Bevelled  Edge-  Projection 
into  the  Sheer  on  Bow  Lines —Expansion  of  Moulded  Edge  on  Bow 
Lines — Stern  Cant  Frames — Projection  of  the  Moulded  Edge  into 
the  Sheer  —Projection  of  the  Bevelled  Edge  into  the  Sheer— True 
Form  of  the  Moulded  Edge  in  the  Sheer  -True  Form  of  the 
Bevelled  Edge  in  the  Sheer— Lifting  Bevels — Moulds  ...         ...    pp.  27—33 

Chapter  III.— Decks. 

Beam  Camber  Allowed— Method  of  Laying  it  Off— To  Draw  in  the  Deck 
at  Side  Line.— Expansion  of  the  Deck  Surface— Method  of  Laying- 
off  Tapered  Stringer  Plate-  Deck  Plate  Edges— Wide  Stringer 
Plates pp.  34—36 


VI  CONTENTS. 

Chapter  IV.— Floors  and  Double  Bottoms. 

Turned-up  Floors — To  Obtain  the  Form — Diminishing  Line — Fairing. 
up — Extreme  End  Floors  — Expansion— Cellular  Double  Bottoms  — 
To  Obtain  and  Fair  the  Double  Bottom — Expansion  of  the  Inner 
Bottom— Expansion  of  the  Margin  Plate — Obtaining  Tank  Knees  — 
Abaft  and  Forward  of  Double  Bottom — Expansion  of  Double 
Bottom  Floors — Mclntyre  Tank — Swan  Conical  Tank  ...    pp.  37  —  44 

Chapter  V. — Shell  Plating. 

Shell  Plating — Obtaining  Sight  Edges— Lining  the  Model  OH'  Fairing 
the  Sight  Edges  on  the  Model,  on  the  f  Lines,  on  the  Loft 
Floor. — Transferring  the  Sight  Edges  to  the  Scrieve  Board — 
Ordinary  Shell  Expansion — Area  of  the  Outer  Bottom— Ordering 
Shell  Plating— Stern  Expansion — Obtaining  True  Form  of  Plating -r 
Check  on  the  Expansion — Another  Method  of  Stern  Expansion — 
Tumble-home  Stern  Expansion      ...         ...  ...         ...         ...    pp.  45 — 53 

Chapter  VI. —Scrieve  Board. 

Scrieve  Board — Information  placed  upon  it  — Its  Purpose— How  Pre- 
pared—Scrieving  in  Frames— Decks — Shell  Plating  Sight  Edges — 
Shell  Plating  Inner  Edges— Ribbands — Keelsons — Floors— Cant 
Knees — Lifting  Beams  -  Frame  Bevels — Applying  Bevels  — Checking 
Bevels — Handy  Bevelling  Machine —Machine  Bevelling         ...    pp.  54—66 

Chapter  VII. — Ribbands  and  Harpins. 

Ribbands— Form  of  a  Ribband  Line— Stem  Termination-  Stern 
Termination— Laying  them  Off  and  Marking  Battens— Deck  and 
Inner  Bottom  Ribbands — The  Common  Harpin  —  Form  of  Moulded 
Edge— Form  of  Bevelled  Edge— The  Sheer  Harpin — Form  of 
Moulded  Edge— Form  of  Bevelled  Edge —Bevelling  Board — Expan- 
sion of  Moulded  Edge  in  Sheer — The  Stern  Harpin— Form  of 
Moulded  Edge — Form  of  Bevelled  Edge pp.  67—73 

Chapter  VIII. —  Moulds. 

Principal  Moulds  and  the  Order  they  are  sent  into  the  Yard  Stem- 
Stern  Frame -Shaft  Struts— Stern  Tubes— Flat  Plate  Keel-- 
Centre  Through  Plate  Keelson— Boat  Beams     pp.   74—84 

Chapter  IX.     Poop  Round  and  Turtle  Back. 

Poop  Round— Obtaining  Lines  and  Fairing-up — Expansion  of  Plating 
— Turtle  Back — How  to  Obtain  and  Fair-up  the  Form — Expansion 
—Plate  Edges pp.  85— 87 

Chapter  X. — Expansion  of  Stringer  Plate  and  Beam   Knees. 

Expansion  of  Stringer  Plate  with  no  Sheer,  and  with  Sheer — Template — 

Allowance  for  Knees  in  Ordering  Tee  Beams,  and  in  Bulb  Plates    pp.   88-90 


CONTENTS.  Vll 

Chapter  XI. — Iron  and  Steel  Masts. 

How  to  Obtain  the  Form — Expansion — Doubling  at  Deck — Doubling 

at  Heel— Mast  Tube  Expansion     ...  pp.  91—95 


Chapter  XII. — Miscellaneous. 

Rudder  Trunk — Obtaining  Form — Expansion — Iron  Deck  House — Form 
and  Expansion — Cargo  Hatch  Coamings  of  Ordinary  Type — Form 
and  Expansion — Cargo  Hatch  Coamings  with  Bell  Mouth  Bottoms 
— Form  and  Expansion — Marking  Off  the  Hawse  Pipes — Cutting 
Holes  — Moulds — Shaft  Tunnel  of  a  Single  Screw— Obtaining 
Form — Expansion — Calculation  for  Round — Marking  Off  the 
Freeboard  in  Screw  Steamer,  in  Sailing  Ship — Finding  Depth 
Moulded  of  a  Ship  when  Dry,  when  Afloat  — Clipper  Stem — Trail 
Board — Figure  Step — Lacing  Piece — Moulds  for  Carver — Fore- 
castle head — Setting  Off  Draught  Marks  on  Stem  and  Stern — Oval 
Manhole— Methods  of  Marking  Off  pp.  96— 113 


WAR  VESSELS. 

Chapter  XIII. — Armour. 

Protective  Deck  in  a  Cruiser — To  obtain  the  Form — Fairing-up  the 
Form  -Ordinary  Expansion —More  Correct  Method  of  Expansion — 
Mode  of  Plating — Model  of  Deck — Bevels  for  Beams — Belt  Armour 
and  Deck  in  a  Battle  Ship — General  Description  of  the  Structure — 
Correction  on  Loft  Floor  for  Belt  Armour  in'  Fairing-up  the 
Moulded  Form — Belt  Deck — Its  Support — Connection — Butts  and 
Seams — Belt  Armour  on  Box  Framing — Armour  Shelf — Protective 
Deck  at  Ends  in  a  Battle  Ship — Finish  of  Belt  Armour  at  the 
Ends  —Fairing-up  the  Belt  Armour — Expansion — Moulds  Required 
for  Ordering  Plates — General  Description  of  the  Structure  of 
Barbettes  or  Redoubts  -Expansion  of  the  Armour — Ordering  the 
Armour — Moulds  Required — Expansion  of  Inner  Thick  Plates  — 
Circular  Barbette — Revolving  Turret  in  Redoubt         ...  pp.   114 — 126 


Chapter  XIV. — Shell  Plating  and  Bilge  Keels. 

Outer  Bottom  Plate  Edges  of  a  Battle  Ship. — Outer  Bottom  Plate 
Edges  of  a  Cruiser  — Bilge  Keels — Where  Best  Placed— Bossed 
Frames  Forward  in  Way  of  the  Ram       ...         ...         ...  pp.   127 — 129 


Chapter  XV. — Double  Bottoms. 

To  Obtain  and  Fair  the  Lines  of  the  Inner  Bottom  of  a  Cruiser — 
Expansion  of  the  Inner  Bottom  -  Expansion  of  the  Longitudinals — 
Expansion  of  a  Longitudinal  on  Curved  Diagonals — Mocking-up 
System  of  Expansion — To  Obtain  and  Fair-up  the  Inner  Bottom 
Lines  of  a  Battle  Ship — Expansion  of  the  Inner  Bottom — Bevels 
on  Inner  Bottom  Frames     ...         ., pp.   130 — 140 


Viii  CONTENTS. 

Chapter  XVI. — Gun  Galleries  or  Sponsons. 

Obtaining  and  Fairing  Lines  of  Midship  Gun  (iallery— Expansion- 
Obtaining  and  Fairing  Lines  of  Midship  Gun  Gallery  of  Conical 
Type— Expansion  of  Conical  Type— Semi  Egg-shaped  Forward 
Gun  Embrasure— Another  Form  of  End  Gun  Gallery— Expansion 
of  End  Gallery  pp.   141—146 

Chapter  XVII.  —Moulds. 

Principal  Moulds,  and  the  Order  they  are  sent  into  the  Yard— Stern 
Posts  —  Stems  —Stern  Tubes— Struts  — Beam  Camber— Conning 
Tower— Pilot  Bridge— Boat  Davits  and  Chocks pp.    147—151 

Chapter  XVIII.  —  Draught  Marks. 
To  Obtain  and  Line-off  the  Draught  Marks  on  Stem  and  Stern      pp.   152—153 

Chapter  XIX.— COMPOSITE  VESSELS. 

Sheer  Draught — Extreme  Form  for  the  Calculation  of  Displacement — 
To  Find  the  Heel  of  Frames  by  Approximate  Method— Exact 
Method  of  Finding  Heel  of  Frames— To  Find  the  Middle  Line  of 
Rabbet— To  End  a  Level  Line  in  Half  Breadth— To  Terminate  a 
Frame  in  Body — To  Find  Bearding  Line  Approximately — To  Find 
the  Middle  Line  of  Rabbet  Accurately— To  Find  the  Bearding 
Line  by  Another  Method— Form  of  Rabbet  in  Main  Keel  Piece- 
Working  Base  Line   pp-   154  —  159 

Chapter  XX. -SHEATHED  VESSELS. 

Alteration  of  Practice— Thickness  of  Wood  Sheathing— Thickness  of 
Shell  Plating— Method  of  Fastening— Solid  Stems  and  Stern  Posts 
—Hollow  Section  Stems  and  Stern  Posts— Method  of  Housing, 
Planking  and  Shell  Plating— Connection  of  Keel— Finish  of 
Planking  and  Plating  on  the  Stern— Stern  Post  of  a  Cruiser— Stem 
of  a  Cruiser— Shaft  Brackets  or  Struts— Method  of  Attachment  at 
Heel  and  Foot— Necessary  Moulds— Stern  Tubes  in  Twin  Screws- 
How  to  House  Planking  and  Shell  Plating— Bossing  of  Frames- 
Necessary  Moulds— Stern  Posts  in  Single  Screws— System  of 
Terminating  Planking,  Shell  Plating  and  Keel— Necessary 
Moulds— Rabbet  in  Main  Keel  Piece— Taking-otf  Planking  and 
Plating PP-   160-164 


■- 


LIST   OF   ILLUSTRATIONS. 


MEKCANTILE   VESSELS. 

FIG.  PAGE. 

1  Sheer  Draught  of  a  screw  steamer       ...  ...         ...         ...  2 

2  ,,  ,,         sailing  ship             ...         ...         ...         ...  2 

3  Laying-Off  on  the  loft  floor        ...  ...         ...         ...         ...  2 

4  Length  between  perpendiculars  ...         ...         ...         ...  4 

5  Section  showing  terms  used      ...         ...  ...         ...         ...  5 

6  Twin  screw  bossing          ...         ...         ...         13 

7  „          „                     14 

8  Single  screw  bossing        ...  ...         ...         ...         ...         ...  15 

9  Finish  of  the  after  end    ...  ...         ...         ...         ...         ...  16 

10  „           „           „           16 

11  ,,          »>           ,,          16 

12  Fairing  up  the  stern         ...         ...         19 

13  Termination  of  the  diagonals    ...  ...         ...         ...         ...  21 

14  Sheer  plan 22 

15  ,,    diagram       ...         ...         ...         ...         ...  22 

16  „          „            23 

17  „          „            24 

18  „           ,,             25 

19  „             25 

20  Cants  in  the  fore  body     ...         28 

21  „           „           „             29 

22  ,,  ,,           ,,             ...         ...         ...         ...         ...         ...  30 

23  ,,  ,,           ,,             ...         ...         ...         ...         ...         ...  31 

24  ,,          after  end           ...         ...         ...         ...  32 

25  Camber  form          ...         ...         ...         ...  34 

26  „           „              34 

27  „           „              34 

28  „           ,,              34 

29  Deck  at  side  on  camber  curve  ";..  ...         ...         ...  34 

30  Tapered  stringer  plate    ...  ...         ...         ...         ...         ...  36 

31  Deck-plating  edges  ...         ...         ...         ...         ...         ...  36 

32  „                „             36 

33  Wide  stringer  plates        ...  ...         . .           ...         ...         ...  36 

34  Curved  floors         ...         ...         ...         ...         ...  37 

35  Extreme  end  floors  sailing  ship  ...         ...         ...         ...  39 

36  ,,  ,,           screw  steamer       ...         ...         ...         ...  40 

37  Cellular  double  bottom 42 

38  Double  bottom  margin  plate     ...  ...         ...         ...         ...  43 

39  ,,  ,,        expansion           ...         ;..         ...         ...         ...  42 


FIG.  PAGE 

40  Shell  plating  sight  edges            45 

41  Marking-off  model  ...          ..         ...         ...         ...         ...  46 

42  Shell  expansion     ...  ...          ...         ...         ...         ...         ...  48 

43  Area  of  the  outer  bottom  plating  ...         ...         ...         ...  49 

44  Expansion  of  a  shell  plate  ...         ...         ...         ...         ...  50 

45  Stern  expansion    ...  ...          ...         ...         ...         ...         ...  51 

46  „             „            52 

47  „             „            53 

48  Scrieve  board        ...  ...                    ...         ...         ...  54 

49  Section  showing  diagonals  ...         ...         ..           ...         ...  .16 

50  Lifting  beams        ...  ...         ...         ...         ...         ...         ...  59 

51  ,,       bevels  of  frames  ..         ...         ...         ...         ...  60 

52  Frame  bevels  ...          ...         ...          ...         ...         ...           ..  61 

53  Bevel  board  ...          ...         ...         ...         ...         ...          ...  62 

54  Bevelling  machine  ...         ...         ...         ...         ...         ...  63 

55  Section  showing  application  of  bevels  ...         ...         ...  63 

56  Detective  bevel  machine  ...         ...         ...         ...         ...  64 

57  Bevelling  machine  ...           .           ...         ...         ...         ...  65 

58  Machine  bevelling  ...                     ...         ...         ...         ...  66 

59  Common  harpin      ..  ..           .  .         ...         ...         ...         ...  69 

60  Harpin  bar ...  ...         ...         ...         ...         ...          ...          ...  69 

61  Application  of  bevel  ...           ..          ...         ...         ...         ...  69 

62  Bevelling  board    ...  ...         ...         ...         ...          ...         ...  69 

63  Sheer  harpin  ...         ...         ...         ...          ...         ...         ...  70 

64  Bevelling  board     ...  ...         ...         ...         ...         ...         ...  71 

65  Stern  harpin  ...          ...         ...          ...          ...         ...         ...  73 

66  Stem  foot  connection       ...  ...         ...         ...         ...          ...  75 

67  ,,      mould           76 

68  ,,      foot  connection       ...  ...          ...         ...          ...         ...  77 

69  Connection  of  keel  and  stem     ...  ...          ...         ...         ...  78 

70  Strut  moulds          ...  ...          ...          ...          ...          ...          ...  78 

71  Stern  tube  moulds  ...         ...         ...         ...         ...         ...  79 

72  „        „         „                 80 

73  Keel  scrieve  board  ...         ...         ...                     ...         ...  81 

74  „         „           „                81 

75  ,,     mould            82 

76  Centre  keelson  mould       ...  ...          ...          ...          ...          ...  82 

77  Boat  beam  mould  ...         ...         ...          ...         ...         ...  84 

78  Poop  round  ...         ...         ...          ...         ...         ...          ■-.  86 

79  Expansion  of  poop  round  ...          ...         ...         ...         ...  86 

80  Turtle  back             87 

81  Expansion  of  stringer  plate        ...  ...         ...         ...         ...  89 

82  Beam  arms  ...         ...         ...         ...         ...         ...         ...  90 

83  „         „                90 

84  „         „               90 

OO  )j                    J,                                     ...                     •••                    ■••                     •••                     ...                     •■•                     •«•  "v 

86     Masts          91 


XI 


Fig. 

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130a 


Mast  heel  doubling 

,,  deck  tube... 
Rudder  trunk 

,,  ,,      expansion... 

»  )!  J> 

Iron  deck  house     ... 
Cargo  hatch  coamings 
Bell  mouth  cargo  hatches 
Hawse  pipes 
Shaft  tunnel 
Freeboard  marks  ... 

,,  ,, 

Marking-off  freeboard 
Finding  depth  moulded  at  ship 
Clipper  stem 

Section  through  cut-water 
Figure  step 

, ,       head  block 
Outline  ship  on  blocks     ... 
Section  showing  sight  board 

Oval  ...         

Forming  oval 

Machine  for  forming  oval 


WAR  VESSELS. 

Body  plan,  showing  protective  deck    ... 

Sheer,  showing  protective  deck 

Detail,  protective  deck  connection 

Sheer,  protective  deck 

Expansion  protective  deck 

Butts  of  protective  deck  plating 

Seams  ,,  ,, 

Finish  ,,  ,,  at  stem 

Box  framing  behind  side  armour 

Body  section  (side  armour) 

Fore  and  aft  sectional  elevation  of  end  armour 

Cross  section  of  end  armour 

Plan  of  finish  of    , ,  , , 

Longitudinal  sectional  plan  of  side  armour 

Laying-off  side  armour     ... 

Expansion    ,,         ,, 

Finish  of  side  armour  at  top 

,,  ,,  bottom 

Barbette,  elevation  and  plan     ... 
Battle  ship's    , ,  , , 

Expansion  of  barbette  armour 

Section  through  thin  plating  at  seams 


PAGE 

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XII 

FIG  1'agJS, 

131  Circular  barbette 126 

132  Revolving  turret -, 126 

133  Battle  ship  s  shell  plating  edges     body  plan...         ..  ..  127 

134  Cruiser's  shell  plating  edges— body  plan        128 

135  Horizontal  section  through  forward  bossed  frames  ...         ...  128 

136  Body  sections,  showing  double  bottom  ...         ...         ...  130 

137  Fairing  lines  for  ,,  ,,  131 

138  Expansion  of  longitudinal  ...         ...         ...  131 

139  Body  for  expansion  of  longitudinal  on  curved  diagonals     ...  134 

140  Expansion  lines  of  longitudinals  on  ,,  ,,  ...  134 

141  Expansion  of  longitudinals  on  ,,  ,,  ...  134 

142  Body  sections,  showing  longitudinal  ...         ...         134 

143  Longitudinal  mould         ...         ...  ...         ...         ...         ...  135 

144  Battle  ship's  body  plan,  showing  double  bottom     ...         ...  136 

145  Lines  for  fairing  double  bottom,  battle  ship  ...         ...         ...  138 

146  Expansion  of  inner  bottom  battle  ship  ...         ...         ...  138 

147  Battle  ship's  midship  section     ...         ...         •••  1-40 

148  Midship  gun  gallery       •• 142 

149  ,,  ,,  of  conical  type     ...         ...         ...         ...  143 

150  Semi  egg-shaped  gun  embrasure  ...         ...  144 

151  End  gun  gallery 145 

152  Stern  post  mould 148 

153  Stem  mould  148 

154  Stern  tube  mould ...  148 

155  Conning  tower  mould 150 

156  Draft  marks  in  war  vessels         ...         ...         •••  153 

COMPOSITE  VESSELS. 

157  Finding  heel  of  frames    ...         ...         ...         ...         ...         ...  154 

158  Middle  line  of  rabbet       156 

159  Boundary  line,  etc.  156 

160  Middle  line  of  rabbet       156 

161  Form  of  rabbet  in  main  keel  piece       158 

SHEATHED  VESSELS. 

162  Stern  post  of  cruiser         160 

163  Stem  „  160 

164  Stints  ,,  161 

165  Palm  of  strut   ,,  162 

166  Stern  tube        ,,  163 

167  Stern  post         ,,  164 

lfiS  .  .         ...         ...         •■•         164 

169  Section  through  main  keel  of  cruiser 163 


f^         OF  TEE  ' 

UNIVERSITY 


NAVAL    ARCHITECTURE. 


MERCANTILE    VESSELS. 


CHAPTER  I. 

Explanation  of  the  Sheer  Draught :  Profile— Half  Breadth — Body  Plan — Lines 
Composing  these  Plans — How  they  appear  in  the  Sheer  Draught — True 
Form  of  the  Lines — Particulars  given  to  Lay  the  Ship  Down — Explan- 
ation of  Terms — Length  Over  All — Length  between  Perpendiculars  — 
Midship  Section  —Moulded  Beam — Moulded  Depth — Rise  of  Bottom — 
Tumble-home—  Deadflat — Turn  of  Bilge  — Camber  of  Beam  — Fore-foot  — 
Depth  of  Hold — Change  of  Frames—Classification  Length  and  Depth  — 
Flam.  Laying-off  the  Vessel  on  the  Loft  Floor :  Mode  of  Procedure — 
Drawing  in  the  Profile— Body  and  Half  Breadth  Plans,  Fairing-up  the 
Body  Plan — The  Best  Lines  for  Fairing-up  —  Projection  of  Bilge 
Diagonal — Definition  of  Fairness — Definition  of  a  Fair  Line — Use  of 
Diagonals— Raised  Keel— Final  Test  of  Fairness — Fairing  by  Contraction 

—  -Definition  of  a  Bow  Line  and  Buttock — Definition  of  a  Bilge  Diagonal 

—  Twin  Screw  Bossing — Twin  Screw  Bossing-covered  Shaft — Bossed 
Frames  Aft— Finish  of  the  After  End — Fairing-up  the  Stern — Diagonal 
Line  Cutting  Knuckle — To  Fair  Frames  from  the  Transom  by  a  Diagonal 

—  To  Fair  Frames  from  the  Knuckle  by  a  Diagonal— Sheer  Line- 
Approximate  Sheer  — Construction  of  Sheer  Diagram — Another  Method 
of  Constructing  Sheer  Diagram — Lowest  Point  of  the  Sheer — Ready 
Method  of  finding  Sheer  Line  -  Sheer  under  Freeboard  Tables — Messrs. 
Swan  &  Hunter's  Method  of  Laying-off". 


LAYIN"G-OFF  THE  SHEER  DRAUGHT  ON 
THE   LOFT   FLOOR. 

The  term,  Laying=off,  is  used  to  express  the  method  adopted 
for  enlarging  and  fairing  the  vessel's  outward  form  to  full  size  on  the 
loft  floor,  or  on  paper  in  the  office,  on  a  larger  scale  than  the  original 
design. 

The  drawing,  from  which  the  particulars  are  taken,  for  laying-off 
the  vessel  on  the  loft  floor  is  the  Sheer  Draught,  which  is 
composed  of  three  plans,  the  Profile  or  Sheer,  the  Half  Breadth  plan, 
and  the  Body  plan,  showing  the  moulded  form  of  the  vessel,  that  is, 
the  form  to  the  outside  of  the  iron  or  steel  frames.  In  wood, 
composite,  or  sheathed  vessels,  this  plan  is  made  to  the  outside  of 
the  planking  for  the  purpose  of  calculating  the  displacement.  It 
may  he  to  any  suitahle  scale  ;  the  usual  is  a  quarter  of  an  inch  equal 
to  one  foot. 

2 


NAVAL  ARCHITECTURE. 


The  Profile,  usually  called  the  Sheer,  is  a  longitudinal  elevation 
with  the  stem  placed  to  the  right  hand  side.  It  shows  the  sheers  of 
the  rail,  knuckle,  and  decks  ;  the  positions  of  the  frame  stations  or 
sections,  and  the  level  or  water  lines  ;  the  form  of  the  ship  at  the 
centre  line,  and  at  fixed  longitudinal  vertical  planes,  parallel  to  the 
centre,  called  bow  and  buttock  lines. 

The  Half  Breadth  plan,  made  for  the  port  side  only,  represents 
the  form  of  the  rail,  knuckle,  and  deck  in  plan  ;  the  longitudinal 
horizontal  shape  of  equidistant  parallel  planes  from  the  top  of  the 
keel  to  the  assumed  load  line,  or  parallel  to  a  fixed  load  line  ;  also, 
the  position  of  the  frame  stations,  the  buttocks,  and  how  lines. 

The  Body  plan  is  the  shape  of  the  vessel  at  transverse  vertical 
planes,  at  different  frame  stations  in  the  length,  taken  square  to 'the 
keel  and  the  centre  line,  upon  which  is  also  indicated  the  decks,  rail, 
and  knuckle.  In  the  case  of  yachts,  war  vessels,  and  others  with  a 
fixed  trim,  the  frames  are  made  square  to  the  load  line.  These 
sections  show  the  shape  of  the  vessel  for  one  side  only.  Those  which 
come  abaft  of  the  midship  section  being  shown  on  the  left  hand  side 
of  the  centre  line,  and  those  forward  on  the  right  hand  side. 

Fig.  i  is  the  Sheer  Draught  of  a  small  screw  steamer,  with  a 
raised  keel,  where  the  frames  are  square  to  the  load  line. 

Fig.  2  is  that  of  a  sailing  ship  on  a  level  keel.  This  plan  is 
COMPOSED  of  the  following  :—  Rail,  knuckle,  deck,  and  level  or  water 
lines,  frame  stations  or  sections,  buttock  and  bow  lines,  diagonals,  and 
the  midship  form. 

They  appear  in  the  drawing  as  follows  : — 


Lines. 

In  Profile. 

In  Half  Breadth. 

In  Body. 

Rail      ... 

Curved... 

Curved... 

Curved. 

Knuckle 

Deck 

Level  or  water 

,,       ...         ... 

Straight 

J, 

5  »              ...                    ... 

,5 

3  > 

Straight. 

Buttocks  &  bow 

Curved  .. 

Straight 

Diagonals 
Frame  stations 

Straight 

Curved... 

Straight 

Curved. 

Their  true  form  is  seen  as  follows 


ft 

In  Profile. 

In  Half  Breadth. 

In  Body. 

Bow  lines  ... 
Buttocks    ... 

Water  lines 
Diagonals 

Frame  stations  or 
sections. 

Rail,  knuckle,  and  deck. 

Il 


l3 


JNE 


LINE 


■  LINE 


-*£ 


BODY      PLAN. 


fi  ;.  i. 

SHEER       IRAUGHT. 


SITY 


' 


BODY      PLAN. 


FIG.  2. 

SHEER     DRAUGHT. 


HALF     BREADTH      PLAN. 


LAYING-OPF  THE  SHEER  DRAUGHT.  3 

It  is  not  customary  in  merchant  work  to  give  the  loftsman  a  copy 
of  the  Sheer  Draught,  but  the  following  particulars  are  supplied,  in 
what  is  called  the  loft  book,  to  lay  the  vessel  down  : — 

The  length  over  all,  length  between  the  perpendiculars,  moulded 
beam,  moulded  depth,  rise  of  the  bottom,  and  fall  in  of  the  bilge 
amidships,  tumble-home  at  the  deck,  size  of  the  forgings  (including 
the  keel),  particulars  of  the  boss  and  the  centre  of  the  screw  shaft, 
form  of  the  extreme  ends  in  Profile  and  Half  Breadth,  sheer  heights 
and  half  breadths  on  the  rail,  knuckle,  and  deck,  half  ordinates  on  the 
water  lines  and  diagonals,  buttock  and  bow  line  heights  on  the  ordinate 
or  frame  stations,  position  of  the  frame  stations,  water  lines,  buttocks, 
bow  lines,  diagonals,  and  deadflat,  rise  of  keel  (if  any),  distance  apart 
and  size  of  frame  and  reverse  bars,  camber  of  beam. 

Before  proceeding  further  it  will  be  best  to  give  a  brief  explana- 
tion of  the  terms  used. 

Length  over  all  is  the  level  length  from  the  extreme  point  of 
the  stern  to  the  fore  end  of  the  figure  head,  or  the  extreme  point  of 
the  stem. 

Length  between  Perpendiculars  (see  Fig.  4).  1.  Case  of 
perpendicular  stem  and  stern  posts.  The  length  is  the  level  distance 
from  the  after  side  of  the  stern  post  to  the  fore  side  of  the  stem  in 
line  of  the  upper  deck.  2.  Case  of  a  raked  straight  stem  or  stern 
post.  Produce  the  fore  side  of  the  stem  and  the  after  side  of  the 
stern  post  until  the  lines  cut  the  upper  deck.  Drop  perpendiculars 
from  these  points,  then  the  level  distance  between  them  is  the  length. 
3.  Case  of  a  curved  or  clipper  stem.  Produce  the  lower  portion  of 
the  stem,  below  the  cut-water,  in  the  same  direction  until  it  cuts  the 
line  of  the  upper  deck  and  the  same  with  the  after  side  of  the  stern 
post.  Drop  perpendiculars  from  these  points,  then  the  distance 
between  such  is  the  length.  4.  Case  of  warships  and  yachts,  the 
length  is  taken  on  the  load  line  from  the  aft  side  of  the  stern  post 
to  the  fore  side  of  the  stem.* 

Midship  Section  is  the  fullest  part  of  the  ship,  and  is  generally 
placed  midway  between  the  perpendiculars.  There  are  cases  where 
it  is  nearer  the  stern  than  the  stem.  It  is  supposed  to  be  at  the 
lowest  point  of  the  sheer. 

Moulded  Beam  is  the  greatest  width  of  the  ship  from  heel  of 
frame  to  heel  of  frame  on  the  midship  section  (see  Fig.  5). 

*  The  length  between  perpendiculars  and  depth  moulded  in  an  awning- 
decked  ship  is  invariably  taken  to  the  deck  below  the  upper  or  awning, 
called  the  main  deck. 


LAYING-OFF  THE  SHEER  DRAUGHT.  3 

It  is  not  customary  in  merchant  work  to  give  the  loftsman  a  copy 
of  the  Sheer  Draught,  but  the  following  particulars  are  supplied,  in 
what  is  called  the  loft  book,  to  lay  the  vessel  down  : — 

The  length  over  all,  length  between  the  perpendiculars,  moulded 
beam,  moulded  depth,  rise  of  the  bottom,  and  fall  in  of  the  bilge 
amidships,  tumble-home  at  the  deck,  size  of  the  forgings  (including 
the  keel),  particulars  of  the  boss  and  the  centre  of  the  screw  shaft, 
form  of  the  extreme  ends  in  Profile  and  Half  Breadth,  sheer  heights 
and  half  breadths  on  the  rail,  knuckle,  and  deck,  half  ordinates  on  the 
water  lines  and  diagonals,  buttock  and  bow  line  heights  on  the  ordinate 
or  frame  stations,  position  of  the  frame  stations,  water  lines,  buttocks, 
bow  lines,  diagonals,  and  deadflat,  rise  of  keel  (if  any),  distance  apart 
and  size  of  frame  and  reverse  bars,  camber  of  beam. 

Before  proceeding  further  it  will  be  best  to  give  a  brief  explana- 
tion of  the  terms  used. 

Length  over  all  is  the  level  length  from  the  extreme  point  of 
the  stern  to  the  fore  end  of  the  figure  head,  or  the  extreme  point  of 
the  stem. 

Length  between  Perpendiculars  (see  Fig.  4).  1.  Case  of 
perpendicular  stem  and  stern  posts.  The  length  is  the  level  distance 
from  the  after  side  of  the  stern  post  to  the  fore  side  of  the  stem  in 
line  of  the  upper  deck.  2.  Case  of  a  raked  straight  stem  or  stern 
post.  Produce  the  fore  side  of  the  stem  and  the  after  side  of  the 
stern  post  until  the  lines  cut  the  upper  deck.  Drop  perpendiculars 
from  these  points,  then  the  level  distance  between  them  is  the  length. 
3.  Case  of  a  curved  or  clipper  stem.  Produce  the  lower  portion  of 
the  stem,  below  the  cut-water,  in  the  same  direction  until  it  cuts  the 
line  of  the  upper  deck  and  the  same  with  the  after  side  of  the  stern 
post.  Drop  perpendiculars  from  these  points,  then  the  distance 
between  such  is  the  length.  4.  Case  of  warships  and  yachts,  the 
length  is  taken  on  the  load  line  from  the  aft  side  of  the  stern  post 
to  the  fore  side  of  the  stem.* 

Midship  Section  is  the  fullest  part  of  the  ship,  and  is  generally 
placed  midway  between  the  perpendiculars.  There  are  cases  where 
it  is  nearer  the  stern  than  the  stem.  It  is  supposed  to  be  at  the 
lowest  point  of  the  sheer. 

Moulded  Beam  is  the  greatest  width  of  the  ship  from  heel  of 
frame  to  heel  of  frame  on  the  midship  section  (see  Fig.  5). 

*  The  length  between  perpendiculars  and  depth  moulded  in  an  awning- 
decked  ship  is  invariably  taken  to  the  deck  below  the  upper  or  awning, 
called  the  main  deck. 


\ 


NAVAL  ARCHITECTURE. 


AFTER  ^PERPENDICULAR 


LAYING-OFF   THE    SHEER   DRAUGHT.  5 

Moulded  Depth  is  the  vertical  distance  from  the  top  of  the 
keel — squared  out  to  the  side— and  the  underside  of  the  upper  deck 
stringer  plate  at  the  lowest  point  of  the  sheer  (see  Fig.  5). 

Rise  of  Bottom. — Produce  the  line  of  the  midship  bottom 
to  the  Half  Breadth  perpendicular,  then  the  distance  between  this 
point  and  the  base  line— squared  out  from  the  top  of  the  keel  is  the 
rise  of  the  bottom  (see  Fig.  5).  It  is,  in  most  cases,  straight,  but 
in  war  vessels  or  yachts  it  may  be  round  or  hollow. 

Fig.   5. 


NO  TANK 


Tumble  =  home  is  the  distance  that  the  midship  side  falls  in 
from  the  half  beam  perpendiculars  in  way  of  the  deck  (see  T   in 

Fig.  5). 

Deadflat,  sometimes  marked  38C,  is  the  straightest  part  of  the 
ship's  bottom,  or  the  greatest  section  amidships,  and  the  point  where 
the  frames  change. 


6  NAVAL  ARCHITECTURE. 

Turn  of  Bilge  is  the  curved  part  joining  the  ship's  side  with 
the  flat  of  the  bottom. 

Camber  of  Beam  is  the  '-round  up"  of  the  deck,  sometimes 
called  "  crop." 

Fore = foot,  the  part  connecting  the  keel  to  the  stem. 

Depth  of  Hold  is  the  distance,  at  the  centre  line  on  the  midship 
frame  from  the  top  of  the  double  bottom  plating  to  the  top  side  of 
the  upper  deck  beams,  or,  in  the  case  of  ordinary  tumed-up  floors,  from 
the  top  of  the  wood  ceiling  (see  Fig-.  5). 

Change  of  Frames. — The  bosom  of  the  fore  body  frames  look 
towards  the  midships,  and  the  after  body  frames  do  the  same.  The 
change  takes  place  on  the  midship  frame.  This  is  done  because  of 
the  excessive  bevel  which  would  occur  at  one  end  if  they  all  looked 
the  same  way,  preventing  the  riveting  of  the  shell  flange. 

Classification  Registry  Length  is  taken  in  way  of  the  upper 
deck  from  the  inside  of  the  stern  and  stem  posts  (Fig.  4).  Awning- 
deckers  have  their  length  on  the  deck  below  the  awning  deck. 

Classification  Registry  Depth  is  taken  from  the  top  of  the 
keel  to  the  top  of  the  midship  beam  at  the  centre  line,  except  in  spar 
and  awning-decked  vessels,  when  it  is  taken  to  the  main  deck. 

Flam  is  the  opposite  of  tumble-home,  that  is,  the  fall  out  of  the 
ship's  side.     Seen  in  the  most  of  vessels  at  the  fore  end. 

Having  given  the  meaning  of  terms  used  in  the  loft,  we  shall  now 
proceed  to  explain  the  method  of 

Laying=off  the  Vessel  on  the  Loft  Floor. — The  majority 
of  loft  floors  are  too  short  to  lay  the  ship  down  in  one  length  ;  there- 
fore, it  is  ordinarily  done  in  two  or  three  lengths  by  a  system  of 
overlapping  into  each  length,  which  secures  continuity  of  the  curves, 
or  the  midship  part  may  be  taken  by  itself  and  faired  on  the  con- 
tracted principle  explained  further  on  on  page  10.  Where  the  loft 
is  sufficiently  long  to  take  the  vessel  in  two  lengths,  each  part  laps 
into  the  other  20  or  30  feet  to  secure  fairness  at  the  juncture,  as 
shown  in  Fig.  3. 

Fig.  3  is  a  drawing  showing  Fig.  1  laid-otf  on  the  loft  floor  in 
two  lengths.     The  trace  lines  give  the  cutting  points  or  projections. 

Mode  of  Procedure. — Having  obtained  particulars  of  the  dis- 
placement sections  or  frame  stations,  with  a  figured  sketch  of  the 
stem  and  stern  from  the  ^  inch  scale  Sheer  Draught,  the  first  step  is 
to  see  that  the  base  board  is  straight,  which  may  form  the  centre 
line  of  the  vessel  in  the  plan  and  the  bottom  of  the  keel  in  the  Profile, 
or  a  parallel  line  may  be  drawn  to  it  for  the  centre  and  base. 


LAYING-OFF  THE  SHEER  DRAUGHT.  7 

It  may  be  noted  here  that  the  working  base  line  in  a  vessel  where 
the  frames  are  square  to  the  keel  is  the  top  of  such  keel.  In  vessels 
with  raised  or  cambered  keels  and  frames  square  to  the  load  line, 
such  load  line  is  usually  the  working  base,  although  some  use  the  line 
shown  in  Figs,  i  and  3. 

Drawing  in  the  Profile. — Divide  in  on  the  base  the  position 
of  the  frame  stations,  and  set  up  the  perpendiculars  giving  the  length 
of  the  vessel ;  which  may  be  done  with  the  loft  trammels.  Then 
strike  in,  fore  and  aft,  the  top  of  the  keel,  which  is  the  working 
base,  the  position  of  the  level  or  water  lines,  the  depth  moulded 
line,  and  the  frame  or  ordinary  stations.  Run  in  with  French  chalk 
the  inside  and  outside  edges  of  the  stem  and  fore-foot,  afterwards  the 
stern  and  screw  aperture  with  the  counter.  Above  the  depth 
moulded  line  on  each  frame  station  set  up  the  sheer  or  deck  at  side, 
and  run  fair  line  through  the  spots,  terminating  on  the  inside  of  the 
stem  and  at  the  centre  line  on  the  stern.  This  line  may  need 
correcting  later  on  ;  for  it  will  be  evident  that  the  deck  sheer  at  the 
centre  line  should  be  a  fair  line.  For  this  purpose,  when  the  deck 
line  is  run  in  the  Half  Breadth,  a  camber  mould  is  made  for  the 
midship  beam,  as  explained  on  page  34,  and  the  camber  due  to  the 
full  width  of  the  deck  at  each  station  is  set  up  above  the  side  sheer. 
Should  the  spots  not  give  a  fair  line,  the  side  is  lowered  or  elevated 
to  suit. 

The  method  of  finding  the  sheer  intermediate  spots  when  only 
the  heights  on  the  perpendiculars  are  given  is  explained  on  page 
20. 

The  rail  and  knuckle  sheers,  also  poop  and  forecastle,  if  any,  are 
next  set  off  and  drawn  in. 

The  Body  Plan. — Fix  a  convenient  position  on  the  floor  for  this, 
as  in  Fig.  3,  and  strike  in  the  centre  line  and  the  half  moulded 
breadth  at  each  side,  rise  of  the  bottom,  breadth  of  the  keel,  half 
siding  of  the  stem  and  stern  posts,  position  of  the  buttocks,  bow 
lines,  and  diagonals.  Lift  off  from  the  Profile  the  sheers  for  the 
rail,  knuckle,  and  deck  at  side  ;  and  place  level  lines  in  the  Body, 
through  these  spots,  to  take  the  half  breadths— those  for  the  fore 
body  on  the  right  hand  side  of  the  centre,  and  those  for  the  after 
body  on  the  left  hand  side.  Also  lift  the  height  of  the  frame 
stations  on  the  inside  of  the  fore-foot,  and  the  same  on  the  after 
posts,  and  place  them  in  the  Body  on  the  half  siding  of  the  posts, 
which  gives  terminations  for  the  section  feet. 


8  NAVAL  ARCHITECTURE. 

The  Half  Breadth  Plan. — Now  square  down  from  the  Profile 
into  the  Half  Breadth  the  terminations  of  the  rail,  knuckle  and  deck 
on  the  stern  and  stem  ;  forward,  these  points  will  be  the  inside  of  the 
stem.  Strike  in  the  position  of  the  buttocks  and  bow  lines,  and  set 
off  on  these  the  form  of  the  rail,  knuckle,  and  deck,  aft  of  the  transom; 
and  on  the  forward  terminations  lay-off  the  half-siding  of  the  stem  : 
it  may  or  may  not  vary.  Place  the  half  breadths  given  you  for  the 
rail,  knuckle,  and  deck  on  their  respective  stations,  and  run  lines  to 
these  spots  consistent  with  fairness  ;  some  loftsmen  only  run  the  rail 
and  the  after  knuckle  to  begin.  Then  lift  from  the  centre  line  on  a 
batten  these  faired  widths,  and  transfer  them  into  the  Body  on 
their  respective  sheer  heights. 

Measure  off  in  the  Body  the  half  ordinates  of  the  water  lines, 
diagonals,  the  buttock  and  bow  line  heights  supplied  you,  which 
will  allow  trial  frames  to  lie  drawn  in  consistent  with  absolute 
fairness.     Then  you  may  proceed  to 

Fair = up  the  Body  Plan. — Square  down  from  the  Profile  into 
the  Half  Breadth,  where  the  water  lines  cut  the  inside  of  the  stem  and 
stern  posts,  and  set  off  on  these  the  half -siding  of  the  posts,  which 
will  be  the  terminations  of  the  water  lines.  Strike  in  a  line  amid- 
ships showing  the  half  beam,  which  is  a  fixed  distance  out  for  any 
line. 

Before  explaining  further,  we  may  say  the  best  lines  for  fairing 
the  body  are: — Rail,  knuckle,  bilge  diagonal,  alternate  water  lines — 
embracing  the  greatest  beam  water  line — and  alternate  buttocks  and 
bow  lines,  or  lines  which  are  square  to  the  surfaces  to  be  faired, 
because  they  give  the  nearest  true  form  of  the  vessel,  and,  therefore, 
show  the  true  amount  added  or  taken  off  to  make  line  fair.  The 
buttocks  and  bow  lines  for  the  ends  and  under  the  midship  bottom  ; 
the  water  lines  for  the  sides  amidships  ;  the  bilge  diagonal  is  con- 
sidered very  useful  for  both  purposes,  especially  under  the  counter  ; 
while  a  diagonal  across  the  shoulder  forward  is  better  than  a  bowline. 

Begin  by  projecting  the  Bilge  Diagonal  into  the  Profile 
explained  on  page  9.  This  diagonal  should  be  so  placed  in  the 
Body  that  it  takes  the  transom,  or  an  additional  diagonal  used  doing 
so.  Square  down  into  the  Half  Breadth  its  termination  on  the 
inside  of  the  posts.  Lift  from  the  Body,  on  the  run  of  the  line,  the 
distances  from  the  centre  to  the  half-siding  and  the  different  frames, 
and  transfer  them  into  the  Half  Breadth.  Fair  line  up,  and  make 
any  corrections  in  the   Body.     Several  diagonals  are  shown  dotted  in 


FIC  3. 

LAYING-OFF  ON   THE    LOFT-FLOOR. 


LAYING-OFF  THE  SHEER  DRAUGHT. 


Figs,  i  and  3,  drawn  in  on  this  principle.  You  may  now  lift  half 
ordinates  on  the  greatest  beam  water  line  and  place  them  in  the  Half 
Breadth  and  fair  the  line  up  and  correct  ;  doing  the  same  with 
alternate  water  lines.  When  these  lines  agree  in  fairness  with  the 
Body  sections,  lift  from  the  base  in  the  Body  the  intersection  of  the 
frames  with  alternate  buttocks  and  bow  lines,  and  transfer  them 
into  the  Profile  ;  and  square  up  from  the  Half  Breadth  on  to  their 
respective  water,  diagonal,  deck,  knuckle,  and  rail  lines,  the  inter- 
sections of  the  buttocks  and  bow  lines  you  are  dealing  with,  shown 
by  trace  lines  in  Fig.  3,  and  explained  on  page  11  under  "bow  line  " 
Bend  a  batten  round  the  corresponding  spots  and  fair  in.  Any 
alteration  to  secure  fairness  must  be  made  in  the  other  plans,  and 
when  this  is  done,  and  the  three  plans  are  absolutely  fair  on  these 
lines,  the  remaining  water  lines,  diagonals,  buttocks,  and  bow  lines 
can  be  run  in.  If  the  initial  fairing  lines  are  wisely  chosen  the 
latter  will  give  little  trouble. 

Definition  of  Fairness. — When  the  buttocks,  bow,  and  sheered 
lines  in  the  Profile  ;  the  level,  deck,  knuckle,  and  boundary  lines  in  the 
Half  Breadth  :  and  the  frame  stations  in  the  Body  show  continuous 
curves  without  abruptness,  the  ship  is  fair  :  or,  when  spots  taken  from 
any  two'  plans  and  placed  in  the  third  show  continuity  without 
abruptness.  Until  this  is  the  case  there  must  be  an  interchange  of 
spots  from  one  plan  to  the  other  to  secure  agreement  and  fairness/ 

Definition  of  a  Fair  Line  is  one  pleasing  to  the  eye,  or  one 
which  has  continuity  without  abruptness  ;  in  other  words,  one  which 
gives  a  graceful  form. 

Use  of  Diagonals. — In  many  of  the  large  shipbuilding  establish- 
ments the  I  inch  lines  are  faired  principally  by  diagonals.  The  first 
step  is  to  place  the  diagonals  in  position  in  the  Body  shown  in  Fig.  1 , 
then  to  project  the  points  «,  b,  c,  d,  e,  and  /,  also  cutting  points  with 
buttocks  and  bow  lines  into  the  Profile  and  draw  curves  in,  from  which 
additional  points  between  the  frame  stations  can  be  got  for  the  water 
lines  and  diagonals  in  the  Half  Breadth  by  squaring  down  from  the 
Profile  where  the  diagonal  or  diagonals  cut  the  water  lines,  and  lifting 
the  cutting  points,  like  if  in  the  Half  Breadth,  from  the  Body;  which 
is  done  by  measuring  the  distance  square  out  from  the  centre  to  where 
the  diagonal  cuts  the  water  line  //,  and  transferring  it  on  to  its 
respective  perpendicular  g2,  in  the  Half  Breadth,  squared  down  from 
the  Profile.  It  will  be  evident  that  all  the  diagonals  can  be  readily 
drawn  thus,  in  the   Half  Breadth,  in  conjunction  with  the  frame 


>  ' 


LAYING-OFF  THE  SHEER  DRAUGHT.  9 

Figs,  i  and  3,  drawn  in  on  this  principle.  You  may  now  lift  half 
ordinates  on  the  greatest  beam  water  line  and  place  them  in  the  Half 
Breadth  and  fair  the  line  up  and  correct  ;  doing  the  same  with 
alternate  water  lines.  When  these  lines  agree  in  fairness  with  the 
Body  sections,  lift  from  the  base  in  the  Body  the  intersection  of  the 
frames  with  alternate  buttocks  and  bow  lines,  and  transfer  them 
into  the  Profile  ;  and  square  up  from  the  Half  Breadth  on  to  their 
respective  water,  diagonal,  deck,  knuckle,  and  rail  lines,  the  inter- 
sections of  the  buttocks  and  bow  lines  you  are  dealing  with,  shown 
by  trace  lines  in  Fig.  3,  and  explained  on  page  11  under  "bow  line  " 
Bend  a  batten  round  the  corresponding  spots  and  fair  in.  Any 
alteration  to  secure  fairness  must  be  made  in  the  other  plans,  and 
when  this  is  done,  and  the  three  plans  are  absolutely  fair  on  these 
lines,  the  remaining  water  lines,  diagonals,  buttocks,  and  bow  lines 
can  be  run  in.  If  the  initial  fairing  lines  are  wisely  chosen  the 
latter  will  give  little  trouble. 

Definition  of  Fairness. — When  the  buttocks,  bow,  and  sheered 
lines  in  the  Profile  ;  the  level,  deck,  knuckle,  and  boundary  lines  in  the 
Half  Breadth  ;  and  the  frame  stations  in  the  Body  show  continuous 
curves  without  abruptness,  the  ship  is  fair  :  or,  when  spots  taken  from 
any  two  plans  and  placed  in  the  third  show  continuity  without 
abruptness.  Until  this  is  the  case  there  must  be  an  interchange  of 
spots  from  one  plan  to  the  other  to  secure  agreement  and  fairness. 

Definition  of  a  Fair  Line  is  one  pleasing  to  the  eye,  or  one 
which  has  continuity  without  abruptness  ;  in  other  words,  one  which 
gives  a  graceful  form. 

Use  of  Diagonals. — In  many  of  the  large  shipbuilding  establish- 
ments the  I  inch  lines  are  faired  principally  by  diagonals.  The  first 
step  is  to  place  the  diagonals  in  position  in  the  Body  shown  in  Fig.  1 , 
then  to  project  the  points  a,  b,  c,  d,  e,  and/,  also  cutting  points  with 
buttocks  and  bow  lines  into  the  Profile  and  draw  curves  in,  from  which 
additional  points  between  the  frame  stations  can  be  got  for  the  water 
lines  and  diagonals  in  the  Half  Breadth  by  squaring  down  from  the 
Profile  where  the  diagonal  or  diagonals  cut  the  water  lines,  and  lifting 
the  cutting  points,  like  g'2  in  the  Half  Breadth,  from  the  Body;  which 
is  done  by  measuring  the  distance  square  out  from  the  centre  to  where 
the  diagonal  cuts  the  water  line  g\  and  transferring  it  on  to  its 
respective  perpendicular  g'2,  in  the  Half  Breadth,  squared  down  from 
the  Profile.  It  will  be  evident  that  all  the  diagonals  can  be  readily 
drawn  thus,  in  the   Half  Breadth,  in  conjunction  with  the  frame 


10  NAVAL  ARCHITECTURE. 

cutting  points  taken  from  the  Body.  These  diagonals,  when  so 
drawn,  can  also  be  utilised  for  the  buttocks  and  bow  lines  in  the 
Profile;  for  the  cutting  points  in  Half  Breadth  may  he  squared  up 
unto  the  diagonal  in  the  Profile,  and  also  the  same  points  in  the 
BoJy  projected  into  the  Profile.  This  method  will  be  found  of 
value,  when  the  distance  at  the  ends  is  great  between  the  load  line 
and  the  deck. 

Fig.  3  shows  these  diagonals,  with  level  and  buttock  lines,  pro- 
jected from  the  Body  into  the  Sheer  and  Half  Breadth.  Their  true 
form  is  also  shown.  By  the  trace  lines  and  a  pair  of  compasses  the 
cutting  points  may  be  easily  found. 

Raised  Keel. — In  this  case  (Figs,  i  and  3)  the  frame  stations 
are  square  to  the  load  line,  and  the  top  of  the  keel  is  the  line  for  the 
frame  feet.  Begin  by  striking  in  the  load  line  and  the  perpendiculars 
square  to  it,  and  set  down  below  the  load  line  on  the  fore  perpen- 
dicular the  draft  forward,  and  on  the  after  perpendicular  the  draft 
aft.  Connect  the  two  points  by  a  straight  line  ;  above  this  set  a 
parallel  line  the  depth  of  the  keel.  Fix  the  position  of  the  midship 
frame  6,  and  on  it,  above  the  top  of  the  keel,  set  up  the  depth 
moulded.  Draw  a  line  parallel  to  the  load  line  through  this  point, 
and  line  off  above  it  the  sheer  heights.  Transfer  the  height  of  the 
frame  station  feet  into  the  Body  on  the  half-siding  of  keel,  stem,  and 
stern  posts.  It  is  considered  best  to  use  straight  water  lines  in  the 
Body,  and  in  that  case,  the  after  sections  will  come  partly  below  the 
top  of  the  keel  amidships,  owing  to  the  keel  drooping  ;  otherwise  the 
manner  of  laying-off  is  the  same  as  before  described,  and  shown  in 

Fig.  3- 

Final  Test  of  Fairness. — An  excellent  manner  of  testing  the 
fairness  of  the  finished  laying  down  of  the  moulded  form  when  done 
by  water  lines  and  buttocks,  is  to  project  a  few  diagonals  into  the 
Profile  and  Half  Breadth.  The  system  is  explained  on  page  9, 
under  "  use  of  diagonals,7'  and  is  seen  in  Fig.  3. 

Fairing  by  Contraction. — It  is  customary  in  most  of  the  mer- 
chant shipyards  to  fair  the  midship  portion  in  this  way,  which  requires 
less  room  on  the  loft  floor.  Diagonal  lines,  square  to  the  surface  of  the 
frames  of  the  Body,  are  used  for  this  purpose.  It  may  be  done  on  the 
buttocks,  bilge  diagonals,  and  water  lines.  The  method  is  to  contract 
the  frame  spacing  to  ^,  },  or  h  of  its  actual  distance,  and  upon 
perpendiculars  from  these  points  are  set  off  the  full  distance,  of  each 
frame  station  from  the  base  or  the  half-moulded   beam  line  of  the 


LAYING-OPF  THE  SHEER  DRAUGHT.  11 

Body  (see  A  B,  C  D,  E  F,  and  G-  H  respectively  in  Fig.  2).  Then  a 
batten  is  pinned  to  each  set  of  spots,  and  a  fair  curve  drawn  in.  Any 
necessary  correction  for  fairness  is  transferred  into  the  Body.  This 
process  is  correct  in  principle  and  greatly  facilitates  fairing,  for  the 
ordinate  spots  are  brought  closer  together,  which  increases  the  curva- 
ture ;  therefore,  the  batten  is  more  likely  to  spring  fair,  owing  to  its 
own  rigidity,  than  when  the  spacing  is  wide.  Care  should  be  taken  in 
fairing  the  ends  to  lap  them  into  this  portion  to  give  a  continuous 
fair  surface.  Some  establishments  fair  the  midship  body  up  on  this 
principle  on  the  "  f  inch  lines"  and  only  lay  the  ends  of  the  vessel  off 
on  the  loft  floor. 

Definition  of  a  Bow  Line. — A  bow  line  shows  in  the  Profile  or 
Sheer,  forward  of  midships,  the  moulded  shape  of  the  ship  at  a 
vertical  plane  parallel  to  the  longitudinal  centre  line.  Consult  Figs. 
1,  2,  and  3,  where  it  is  seen  in  its  true  form  in  the  Profile.  To  draw 
it  you  project  from  the  Half  Breadth  the  points  of  intersection  of  the 
line- with  the  water,  rail,  knuckle,  and  deck  lines  on  to  their  corre- 
sponding lines  ;  and  also  level  over  from  the  Body  into  the  Sheer  to 
their  corresponding  stations,  the  cutting  points  of  the  line  and  the 
frame  stations.  It  will  be  seen  from  this  that  a  bow  line  must  cut 
level  and  sheered  lines  in  the  same  place  in  the  Half  Breadth  and 
Sheer  ;  also  the  frames  in  the  same  place  in  the  Body  and  Sheer. 
A  batten  placed  on  the  Sheer  spots  ought  to  give  a  fair  line  if  the 
Half  Breadth  and  Body  are  fair,  if  not,  spots  are  interchanged  until 
the  three  plans  show  joint  fairness.  It  is  customary  in  many  yards 
to  call  this  line'  a  buttock. 

Definition  of  a  Buttock. — A  buttock  is  similar  to  a  bow  line, 
being  a  continuation  of  it,  applying  to  that  part  abaft  of  the  midship 
frame. 

Definition  of  a  Bilge  Diagonal. — A  bilge  diagonal  represents 
the  shape  of  an  oblique  longitudinal  plane,  extending  from  the  centre 
line  of  the  vessel  to  the  turn  of  the  bilge  on  the  midship  frame. 
See  diagonals  2  and  7  in  Figs.  1  and  3  in  Fig.  3.  It  may  be  shown  in 
its  true  form  in  the  Profile  or  Half  Breadth.  The  points  of  intersec- 
tion with  the  half-siding  of  the  stem  or  stern  post  are  projected  from 
the  Body  into  the  Profile  on  the  inside  line  of  the  post,  and  then 
squared  down  on  to  the  base.  A  batten  laid  on  the  run  of  the 
diagonal  in  the  Body  and  the  distance,  from  the  centre,  of  the  half- 
siding  of  post  and  the  frames  marked  upon  it,  and  transferred  into 
the  Half  Breadth  on  corresponding  stations,  through  which  the  curve 


12  NAVAL  ARCHITECTURE. 

is  drawn.  This  is,  perhaps,  the  best  line  for  fairing,  because  it  cuts 
the  surface  usually  at  about  right  angles. 

Twin  Screw  Bossing. — Take  the  simplest  case,  in  Fig.  6,  where 
the  shaft  is  parallel  to  the  centre  of  the  ship  and  the  keel  line. 
Draw  in  the  Body  the  position  of  the  shaft  centre  a,  and  from  it 
describe  a  circle  of  radius  a  b,  the  required  diameter  for  the  tube,  etc., 
i.e.,  a1  b1.  Place  in  the  Body  the  diagonal  A  B  square  to  the  frames 
cutting  a,  the  shaft  centre.  Lift  the  position  of  the  unbossed  frames 
and  the  centre  of  the  shaft,  on  the  direction  of  this  line,  and  place 
them  in  the  Half  Breadth  which  will  give  A1  B1.  Run  in  the  centre  of 
the  shaft,  distance  B  a,  and  parallel  to  the  centre  of  the  ship,  and 
arrange  tube  as  shown.  To  save  inside  bossing  the  after  end  should 
be  fixed  to  allow  nut  on  the  end  of  the  tube  to  clear  ship's  side.  The 
length  is  usually  settled  by  the  engineers.  Set  off  line  c  d  parallel  to 
the  shaft  centre,  showing  the  amount  of  clearance  required  to  draw 
the  tube  and  stuffing  box  gland  out  clear  of  the  frames — allow  a  little 
—then  set  out  from  this  line  the  width  of  the  frame  flange  on,  say, 
frame  15.  Pin  a  batten  to  the  line  A1  B1,  and  let  it  spring  at  the 
after  end  to  points  E,  D,  C,  and  fair  curve  in,  keeping  the  bossed  part, 
consistent  with  a  fair  and  beautiful  form,  as  short  as  possible.  Lift 
the  distances  to  this  curve  from  the  centre  line  of  the  ship,  and 
transfer  them  on  to  the  line  B  A  in  the  Body ;  and  with  the  point  a  as 
centre,  and  these  distances  as  radii  describe  arcs  of  circles,  connecting 
them,  at  the  top  and  .bottom,  with  their  respective  frames  by  easy  radii 
or  curves.  Fair  these  lines  up  with  close  level  lines  in  the  Half  Breadth, 
or  buttocks  in  the  Profile.  Sometimes  diagonal  lines  like  F  G  and 
H  K  are  used.     Their  form  is  shown  in  the  plan  by  F1  G1  and  F2  K1. 

In  case  the  shaft  is  raked  to  the  keel,  and  also  not  parallel  to  the 
centre  line  of  the  vessel,  the  lines  should  be  shown  in  the  Profile  and 
Half  Breadth,  and  the  centre  at  each  frame  placed  in  the  Body,  when 
the  above  method  can  be  proceeded  with. 

Twin  Screw  Bossing — Covered  =  in  Shafts.  — In  some  cases 
the  shaft  is  covered  in  from  the  stern  tube,  shown  in  Fig.  6,  to  the 
after  struts,  with  portable  built  plate  tubes,  but  this  does  not  give 
satisfaction  for  general  purposes.  The  best  mode  seems  to  be  that 
given  in  Fig.  7,  where  the  frames  are  bossed  to  case  in  the  shafts  for 
the  full  length,  and  by  it  easy  access  is  secured  from  the  inside  of  the 
ship.  The  foremost  frames  are  bossed  in  the  usual  way,  and  gradually 
formed  towards  the  fine  ends  into  loops  with  about  2  feet  neck  at  A. 
Where  the   outstretch    is  considerable   the   frames   are   continuous, 


LAYING-OFF   THE    SHEER    DRAUGHT. 


13 


HALF    BREADTH 


CAST  STEEL  R\NQ 


14 


NAVAL  ARCHITECTURE. 


AFTER     BODY     SECTIONS 


as  indicated  by  dotted  lines,  and  short  frames  looking  aft  made  to 
form  the  loop,  which  are  scarphed  at  the  top  and  bottom  to  the 
ordinary  frames.  Partial  bulkheads  or  web-plated  frames  being  fitted 
at  intervals  to  stiffen  the  structure.  It  is  a  common  practice  to 
make  the  after-shaft  brackets  and  the  stern  post  in  one  piece,  and 
rabbet  the  shell  plating  on  to  it. 

To  Obtain  and  Fair  the  Form  in  such  a  case. — The  ordinary 
moulded  form  is  first  faired-up  on  the  loft  floor,  or  the  f  lines.  Then 
the  centre  of  the  shaft  is  shown  on  the  Sheer,  Half  Breadth,  and 

Body.  A  diagonal  line  C  D 
is  placed  in  the  Body  and 
laid  off  in  the  Half  Breadth, 
showing  the  unbossed  mould- 
ed form  of  the  vessel,  and 
the  centre  of  the  shaft  as 
near  as  possible  on  this  dia- 
gonal. The  necessary  dis- 
tance outside  of  the  shaft 
centre,  allowing  for  shafting, 
framing,  and  withdrawing  of 
the  after  tube,  etc.,  is  set  off 
from  the  shaft  centre  at  the 
different  points,  and  a  line 
run  through  the  spots  and 
faired,  which  gives  the  out- 
stretch of  the  bossing  ;  this 
Fig.  7.  is  transferred  into  the  Body. 

A  few  approximate  sections  may  now  be  sketched  in,  allowing 
about  2  feet  neck  at  A  for  getting  at  the  shaft,  etc.  Diagonal 
lines  G  F  and  E  B  are  put  through  the  curves  at  the  top  and 
bottom,  and  faired  in  the  Half  Breadth.  From  these  lines  spots 
are  lifted  for  the  intermediate  frames  in  the  Body,  and  sections 
drawn.  The  whole  may  now  be  faired  by  closely  spaced  radiating 
diagonal  lines  from  the  points  H  and  E,  and  perhaps  a  few  buttocks. 
The  diagonals  should  be  so  placed  that  they  take  in  the  ordinary 
moulded  form  with  the  curves  for  bossing,  to  secure  a  continuous  fair 
surface.  These  frames  are  scrieved  in  on  the  scrieve  board  and 
corrected  bevels  supplied. 

Bossed  Frames  Aft. — In  single  screws  a  few  frames  are  bossed 
just  forward  of  the  screw  post.    This  is  ordinarily  done  in  the  following 


LAYING-OFF  THE  SHEER  DRAUC.HT. 


15 


manner :— After  the  frames  are  serieved  in  to  the  unbossed  form,  set- 
off on  the  centre  line  of  the  Body  in  Fig.  8  the  position  of  the  shaft 
centre  a,  and  from  a  descrihe  semicircle  a  c  showing  the  extreme  radius 


CO 

bi> 
iZ 


LU 


O 

a. 


ISOd    NW31S 


LL 


u 

of  the  boss,  and  draw  in  the  adjacent  form,  according;  to  the  ordered 
stern  frame.  Lift  the  form  of  the  ship  to  the  ordinary  curves,  shown 
dotted,  on  the  level  line  a  b  for  about  ten  frames  from  the  post,  and 


[I 


16  NAVAL  AKCHITECTURE. 

place  the  distances  on  their  corresponding  frames  in  the  Half  Breadth, 
passing  curve  c1  Z*1  through  the  spots.  Draw  in  this  plan  the  after  and 
forward  sides  a1  r2  and  a2  d  of  the  screw  post  boss,  and  of  the  width  of 
radius  a  c.  Connect  c2  to  d  which  will  be  parallel  to  the  centre  line. 
Pin  a  batten  to  the  original  line  b1  c1,  and  then  let  the  batten  spring 
at  the  after  end  sufficient  to  allow  the  aftermost  frames  to  clear  stern 
tube,  for  about  two  or  three  spaces,  until  it  joins  the  point  d.  Fair 
the  line  &1,  d,  c2,  and  transfer  the  altered  form  on  to  the  level  line  in 
the  Body.  Then  from  the  centre  of  the  shaft  a,  with  these  points  as 
radii,  draw  arcs  of  circles,  and  connect  these  arcs  with  their  respective 
frames  at  the  top  and  bottom  by  easy  curves.  Place  level  lines  through 
the  latter,  and  test  their  fairness  in  the  Half  Breadth,  or  fair  up  with 
diagonals 

Finish  of  the  After  End.  —  In  screw  steamers,  different  forms 
are  adopted  on  and  about  the  transom  foot  and  the  arch  of  the  screw 
aperture,  which  occasions  a  slight  difference  in  the  termination  of  the 
lines  to  that  of  vessels  without  apertures.  In  Fig.  9  is  shown  one 
method  with  a  tuck  plate  flanged  on  its  fore  edge  to  take  the  shell 
plating,  as  seen  in  the  Sheer  and  section  through  A  B.  All  the  lines 
terminate  on  the  fore  edge  of  the  propeller  post  produced  to  meet  the 
counter  in  a  fair  curve,  and  at  a  distance  from  the  centre  equal  to  the 
half  thickness  of  the  post — L  M  in  the  Half  Breadth  and  L1  M1  in  the 
Body.  These  points,  a,  b,  c,  d,  e,  and  /,  are  squared  down  on  to  L  M 
for  the  finishing  spots  for  the  level  lines.     The  tuck  plate  is  vertical. 

In  Fig.  10  the  tuck  plate  is  dispensed  with  ;  the  shell  plating 
edges  are  run  out  to  the  after  post,  and  to  break  the  knuckle,  which 
would  be  caused  by  bringing  a  curved  surface  abruptly  on  to  a  flat  one, 
a  small  radius  is  introduced  at  the  line  WAX.  The  shell  plates  are 
set  on  a  half-round  moulding  bar.  To  obtain  the  form  through 
WAX,  several  planes,  like  A  B,  are  taken  square  to  the  line  and  pro- 
duced in  the  other  plans,  by  which  the  form  of  the  section  is  got. 
Produce  points  A,  c,  b,  and  a  in  the  Sheer  to  corresponding  lines  in 
the  Half  Breadth,  namely,  A2,  c,  b1,  a1,  and  draw  line  A'2  B2.  Then 
produce  indefinitely  a  a2,  ff1,  b  b2,  dd\  c  c\  e  e1  square  to  A  B.  Lift 
the  cutting  point  distances  of  the  several  lines  a1,  b\  and  c  square 
from  the  centre  in  the  Half  Breadth,  and  lay  them  out  on  their 
corresponding  lines  in  the  Sheer,  a1  on  a  a2,  b1  on  5  b2,  and  so  on, 
which  will  give  spots  for  the  section  A  B.  Those  for  the  buttocks 
may  be  got  by  placing  the  buttock  lines  parallel  to  A  B,  so  that  they 
cut  their  respective  trace  lines/,  d,  and  e  produced.    Show  in  the  Sheer 


RAIL 


KNUCh 


Z 
LEVE 


LEVE 


LEVEL 


LEVE 


BODY    SECTIONS 


BAIL    LINE 


KNUCKLE    LINE 


SECTION  AT  A.B 


Fig.  9.  SHEER 


CENTRE     LINE    OF    H4LF    BREADtTH  8.  BASE.  LINE  OF  3«fER  1300 


10FT  BUTTOCK 


6FT    PUTTOCK    i.  LEVEL    LINE 


5  FT    BUTTOCK  i.  LEVEL,  LINE    6 


KNUCKLE    LINF 


RAIL     LINE 


WSIDE  STRAKF 


LEVEL  LINE     I 


?<&'     OFTHK  T 

UNIVERSITY 

OF  CAUfO*^ 


Fig.  10 


^^.^p^p 


OF  THE 


UNIVERSITY 


BODY 


Fig.  11. 


SHEER 


LAYING-OFF  THE  SHEER  DRAUGHT.  17 

the  half-siding  of  the  post  S  L.  (See  enlarged  diagram.)  Produce  A  to 
cut  L,  and  extend  the  line  indefinitely.  With  a  small  radius  of  2  to 
4  inches,  equal  P  L,  describe  circle  L  m  n  from  P  to  cut  L.  Then 
the  line  S  L  R  is  joined  with  a  fair  curve  to  e1,  c\  d1,  b2,/1,  etc.,  which 
gives  form  of  plane  A  B.  Referring  to  enlarged  sketch,  place  close 
buttock  lines  in  the  section,  D  and  E,  and  produce  their  cutting  points 
with  SLR  square  on  to  A  B,  m  to  m1  and  n  to  n1 ;  then  m1  and  n1 
are  spots  for  the  close  buttocks  on  A  B.  Buttocks  lines  may  be  lined 
in  above  and  below  this  section  A  B,  cutting  m1  and  n1,  and  gradually 
reducing  the  radius  ;  or  it  may  be  taken  the  full  depth  from  the 
transom  to  the  arch  of  the  post.  It  will  be  evident  that  if  the  close 
buttocks  be  placed  in  the  Half  Breadth  the  form  of  the  level  lines  on 
these  buttocks  may  be  found  by  squaring  down  the  cutting  points,  as 
shown  by  trace  lines.  The  same  applies  to  the  frame  stations  ; 
the  intersections  are  levelled  over  on  to  corresponding  buttocks  in  the 
Body,  and  the  form  of  the  section  drawn  in. 

In  many  twin  screws  the  propeller  blades  cross  the  centre  line  of 
the  vessel,  at  a  short  distance  from  each  other,  which  necessitates  a 
shallow  aperture,  shown  in  Fig.  n.  The  plate  lines  are  carried  to 
the  stern  post  immediately  above  the  arch  of  the  aperture  ;  and  the 
level  lines  terminate  on  the  half  siding  of  the  fore  edge  of  the  stern 
post,  except  in  such  a  case  as  level  line  1  which  terminates  at  c. 

Perhaps  the  easiest  way  to  get  the  suitable  form  of  the  level  lines 
is  to  place  in  the  Body  a  few  closely  spaced  diagonals,  marked  1 ,  2,  3, 
4,  5,  square  to  the  curve  of  the  frames,  about  the  run  of  the  plate 
edges,  which  readily  catch  the  eye  in  looking  along  a  ship's  after 
form.  Lift  the  true  form  of  these  diagonals  into  the  Half  Breadth 
(as  explained  on  page  11),  and  fair  them  carefully.  The  terminating 
points  may  be  got  by  following  the  trace  lines,  a  to  a1,  a1  to  a2,  d  to 
d\  d1  to  dr  on  the  half  siding  of  post ;  and  e  on  the  half  siding  for  8, 
4,  and  5.  When  these  lines  are  faired-up,  the  form  of  every  section 
to  about  six  frame  is  transferred  into  the  Body  on  these  diagonals, 
and  curves  drawn  through  the  spots.  Close  buttock  lines  are  then 
placed  next  the  centre  in  the  Body  and  Half  Breadth,  and  the  cutting 
points,  like  A,  B,  C,  D,  E  on  T,  and  /,  k,  h,  g,f  on  3  frame,  levelled 
over  into  the  Sheer  on  their  corresponding  frame  stations  ;  which, 
with  the  terminations  on  the  knuckle  squared  up  from  the  Half 
Breadth,  enable  the  form  of  the  buttocks  to  be  drawn  in.  The 
fairness  may  be  tested  by  level  lines  in  the  Half  Breadth,  squaring 
down  the  points  as  in  the  case  of  level  line  2,  r,p,  o,  n,  and  m,  giving 

3 


ffgE    UBR4, 

"         OF  THT 

UNIVERSITY 


LAYING-OFF  THE  SHEER  DRAUGHT.  17 

the  half-siding  of  the  post  S  L.  (See  enlarged  diagram.)  Produce  A  to 
cut  L,  and  extend  the  line  indefinitely.  With  a  small  radius  of  2  to 
4  inches,  equal  P  L,  describe  circle  L  m  n  from  P  to  cut  L.  Then 
the  line  S  L  R  is  joined  with  a  fair  curve  to  e1,  c1,  d1,  b2,  f1,  etc.,  which 
gives  form  of  plane  A  B.  Referring  to  enlarged  sketch,  place  close 
buttock  lines  in  the  section,  D  and  E,  and  produce  their  cutting  points 
with  SLR  square  on  to  A  B,  m  to  m1  and  n  to  n1 ;  then  m1  and  n1 
are  spots  for  the  close  buttocks  on  A  B.  Buttocks  lines  may  be  lined 
in  above  and  below  this  section  A  B,  cutting  m1  and  n\  and  gradually 
reducing  the  radius  ;  or  it  may  be  taken  the  full  depth  from  the 
transom  to  the  arch  of  the  post.  It  will  be  evident  that  if  the  close 
buttocks  be  placed  in  the  Half  Breadth  the  form  of  the  level  lines  on 
these  buttocks  may  be  found  by  squaring  down  the  cutting  points,  as 
shown  by  trace  lines.  The  same  applies  to  the  frame  stations  ; 
the  intersections  are  levelled  over  on  to  corresponding  buttocks  in  the 
Body,  and  the  form  of  the  section  drawn  in. 

In  many  twin  screws  the  propeller  blades  cross  the  centre  line  of 
the  vessel,  at  a  short  distance  from  each  other,  which  necessitates  a 
shallow  aperture,  shown  in  Fig.  n.  The  plate  lines  are  carried  to 
the  stern  post  immediately  above  the  arch  of  the  aperture  ;  and  the 
level  lines  terminate  on  the  half  siding  of  the  fore  edge  of  the  stern 
post,  except  in  such  a  case  as  level  line  1  which  terminates  at  c. 

Perhaps  the  easiest  way  to  get  the  suitable  form  of  the  level  lines 
is  to  place  in  the  Body  a  few  closely  spaced  diagonals,  marked  1 ,  2,  3, 
4,  5,  square  to  the  curve  of  the  frames,  about  the  run  of  the  plate 
edges,  which  readily  catch  the  eye  in  looking  along  a  ship's  after 
form.  Lift  the  true  form  of  these  diagonals  into  the  Half  Breadth 
(as  explained  on  page  11),  and  fair  them  carefully.  The  terminating 
points  may  be  got  by  following  the  trace  lines,  a  to  a\  a1  to  a2,  d  to 
d\  d1  to  d2  on  the  half  siding  of  post ;  and  e  on  the  half  siding  for  3, 
4,  and  5.  When  these  lines  are  faired-up,  the  form  of  every  section 
to  about  six  frame  is  transferred  into  the  Body  on  these  diagonals, 
and  curves  drawn  through  the  spots.  Close  buttock  lines  are  then 
placed  next  the  centre  in  the  Body  and  Half  Breadth,  and  the  cuttins; 
points,  like  A,  B,  C,  D,  E  on  T,  and  /,  k,  h,  g,  f  on  3  frame,  levelled 
over  into  the  Sheer  on  their  corresponding  frame  stations  ;  which, 
with  the  terminations  on  the  knuckle  squared  up  from  the  Half 
Breadth,  enable  the  form  of  the  buttocks  to  be  drawn  in.  The 
fairness  may  be  tested  by  level  lines  in  the  Half  Breadth,  squaring 
down  the  points  as  in  the  case  of  level  line  2,  r,p,  o,  n,  and  m,  giving 

3 


18  NAVAL  ARCHITECTURE. 

points  r\  p1,  o\  n\  and  m1.  The  position  of  the  frames  on  the  level 
lines  is  also  lifted  at  the  same  time  from  the  Body,  and  placed  in  the 
Half  Breadth.  Before  drawing  in  the  lines  the  termination  of  each 
level  line  is  squared  down  from  the  Sheer  on  to  the  half  siding,  c  to 
c1  for  level  line  1,  and  e  the  fore  edge  of  the  stern  post  for  the 
remainder  above  the  arch  of  the  aperture.  By  this  means  it  will 
be  evident  that  the  true  form  of  the  level  lines  may  be  found.  The 
close  buttock  lines  have  a  peculiar  character  in  the  Sheer,  but  this 
will  appear  the  most  reasonable  form  when  consideration  is  given  to 
the  fact  that  you  are  dealing  with  a  curved  surface  in  conjunction 
with  a  flat  one. 

In  some  cases  the  buttock  lines  in  the  Sheer  have  an  easier  sweep 
below  the  transom,  regulated  somewhat  by  the  sight  edges  of  the 
plate  lines. 

Fairings  up  the  Stern. — The  stern  overhung  is  sometimes 
faired-up,  after  the  main  Body  is  finished,  on  the  buttocks  and  a  few 
temporary  cross  sections  taken  abaft  of  the  transom.  It  has  to  be 
done  very  carefully,  for  a  badly  faired  stern  spoils  the  look  of  any 
vessel,  or  at  the  least  occasions  unnecessary  packing.  Fig-.  12  shows 
part  of  the  Sheer  Draught  on  the  loft  floor.  Square  up  from  the  Half 
Breadth  into  the  Sheer  the  buttock  intersections  A,  B,  e\  and  D  on  the 
rail  and  knuckle,  then  run  the  centre  lines  in  the  Sheer  E  F  and  Gr  H. 
The  curves  at  the  sides  E  J  and  G  K  are  got  by  finding  the  amount  of 
camber  from  the  beam  mould  in  way  of  each  buttock  and  setting  it 
down  on  the  buttock  perpendicular  from  the  rail  and  knuckle  centre 
lines.  This  camber  may  easily  be  found  by  setting  out  on  the  edge 
of  the  mould  at  each  side  of  the  centre  the  square  distance  of  the 
buttock,  and  stretching  a  line  from  the  two  points,  then  the  camber 
is  the  distance  on  the  centre  from  this  line  to  the  top  of  the  mould. 
For  instance,  the  camber  on  J  F  is  J1  F1.  Draw  the  buttock  lines 
in  straight  from  the  rail  to  the  knuckle,  and  fair  them  in  the  Half 
Breadth  by  placing  level  line  L  M  in  the  Sheer  and  Body  plans,  and 
projecting  into  the  Half  Breadth  the  points  a,  &,  c.  Then  lift  on  the 
level  line  L1  M1,  from  the  centre,  the  distances  of  0,  T,  1  and  2 
frames,  and  place  them  in  the  Half  Breadth.  All  these  spots  are 
usually  adhered  to,  except  that  on  the  buttock  next  the  transom 
which  is  made  slightly  fuller  to  form  a  fair  line  with  the  other  part 
of  the  vessel.     When  faired  the  corrected  points  are  projected  into 

Note. —In  future  reference  the  word  Profile  will  be  dropped,  and  "Sheer" 
used  when  referring  to  it,  which  is  the  common  term. 


LAYFNTG-OFF  THE  SHEER  DRAUGHT. 


19 


the  Sheer,  and  the  alteration  to  buttocks  made.  The  side  lines  for 
rail  and  knuckle  abaft  of  T  are  placed  in  the  Body  by  lifting 
on  the   buttocks  and   stern  the  vertical  distances  of  the  rail  and 


knuckle   side  sheers,  above  and  below   the  level  hue 
L  M,  and  placing  them  on  their  corresponding  lines 
in  the  Body,  through  which  curves  are  drawn. 

The  deck  line  may  be  put  in,  in  the  same 
manner,  by  drawing  in  the  centre,  and  finding 
the  camber  in  the  usual  way.  The  part  below 
the  knuckle  line  is  faired  by  a  few  tempo- 
rary square  frames  placed  abaft  of  the 
transom.  The  heights  of  the  same  on 
the  centre,  buttocks,  and  knuckle  trans- 
ferred into  the  Body,  together  with 
the  half  breadths  on  the  knuckle 
and  rail  from  the  plan,  will  enable 
the  sections  to  be  drawn  in 
approximately.  They  are  then 
transferred,  on  a  few  closely 
spaced  level  lines  marked  1 
and  2,  into  the  Half  Breadth ; 
and  faired-up  on  the  buttocks  in  the  Sheer  in  the  usual  manner. 
Care  must  be  exercised  to  avoid  any  knuckle  on  the  centre  line  of 
the  stern  ;  and  also  to  lap  the  buttocks  fair  into  the  part  forward  of 


3W1N3D 


20  NAVAL  ARCHITECTURE. 

transom  already  faired-up,  which  may  necessitate  a  slight  alteration 
in  the  form  of  the  transom.  This  method  is  carried  out  in  some 
yards  before  the  fairing  up  of  the  main  body,  as  part  of  the  first  steps. 

Diagonal  Line  Cutting  After  Knuckle. — To  project  the 
diagonal  C  A,  shown  in  Fig.  13,  from  the  Body  into  the  Sheer  and 
Half  Breadth.  Lift  the  distances  square  out  from  the  centre  line  to 
the  cutting  points  on  the  frames,  and  lay  them  off  on  their  respective 
stations  in  the  Half  Breadth,  D  B  on  D1  B1,  B1  is  the  termination  on 
the  knuckle  line.  A  curve  drawn  through  spots  should  be  fair,  if  the 
sections  are  fair.  This  line  may  be  projected  into  the  Sheer  by 
squaring  up  the  point  Bl  to  knuckle  B2,  and  E1  on  to  the  buttock 
E2,  and  levelling  over  from  the  Body  the  intersection  of  the  different 
frames,  shown  by  dotted  lines.  Through  the  spots  run  curve,  and 
you  have  the  projection  of  the  diagonal. 

To  Fair  Frames  from  the  Transom  by  a  Diagonal. — This 
is  sometimes  done  by  placing  line  e  F  in  the  Half  Breadth,  e1/1, 
parallel  to  the  centre.  Then  lift  from  e  on  the  run  of  the  diagonal 
the  position  of  the  frames,  and  set  them  out  from  e1/1.  The  line  D 
shows  the  true  form  of  the  ship  from  the  transom  forward,  and 
should  be  a  fair  line  if  the  body  is  fair  ;  but  the  best  plan  is 

To  Fair  the  Frames  from  the  Knuckle  by  a  Diagonal. — 
Lift  D  B  in  the  Body  square  out,  and  set  it  out  on  the  knuckle  D1  B1, 
and  through  the  point  B1  draw  perpendicular  D1  B2.  Then  lay  a 
batten  on  C  A,  and  mark  distances  C  to  B,  C  T,  C  3,  etc.,  and  lay 
them  out  in  the  Half  Breadth,  0  B  on  D1  B2,  which  gives  B3  for 
termination,  the  others  on  their  respective  frames.  Draw  line 
through  spots,  which  should  be  fair  if  the  sections  are  fair.  This 
is  the  true  form  of  the  vessel  on  the  diagonal.  Tf  the  line  is  not 
fair,  fair  it,  and  transfer  alterations  into  the  Body,  and  make 
correction  on  the  buttocks  of  the  Sheer. 

Sheer  Line. — The  mean  sheer  of  the  deck  at  the  side  for  different 
classes  of  vessels  is  given  in  the  "  Freeboard  Tables,"  but  an  approxi- 
mate mean  sheer  in  inches  may  be  found  by  dividing  the  length  in  feet 
between  the  perpendiculars  by  10  and  adding  10.  Take  a  ship  200 
feet  long,  then  the  mean  sheer  is  30  inches,  and  the  united  sheers  of 
the  after  and  forward  perpendiculars  is  twice  30,  which  gives  60 
inches.  The  sheer  aft  is  usually  made  one-third  of  the  total  which 
leaves  two-thirds  for  forward.  In  the  example  taken  it  would  be 
20  inches  on  the  after  perpendicular  and  40  inches  on  the  forward. 
The  lowest  point  of  the  sheer  may  or  may  not  be  on  the  midship 


CD 


"f 


(0 


I  I 


"o\ 


>ooiina 


'I     I 


y 


A&_ 


22 


NAVAL  ARCHITECTURE. 


to 


<*    D£ 


be  x 
iZ  w 


ID 


fO 


frame.  The  points  in  between  the  lowest  point 
and  the  perpendiculars  are  got  by  two  or  three 
different  methods,  the  most  nsefnl  being  a  sheer 
diagram  which  may  be  brought  into  use  when  once 
made  for  any  ship,  drawn  at  any  scale,  within  its 
limits. 

Construction  of  a  Sheer  Diagram.— Draw  in 
the  Sheer  plan,  Fig.  14,  the  depth  moulded  line  A  B 
extending  from  the  after  to  the  forward  perpendiculars, 
and  divide  the  length  into  a  suitable  number  of  equal 
spaces,  say  16  parts,  and  produce  the  points,  square  to 
A  B,  indefinitely  above  the  line.  Call  the  lowest  point 
of  the  sheer  0,  and  number  the  stations  abaft  and 
forward  of  this  1,  2,  3,  4,  5,  6,  7,  and  8  respectively. 
Then  in  Fig.  15  on  the  base  C  A  erect  a  perpendicular, 
A  B.  Let  the  base  C  A  stand  for  0  station,  then 
square  each  of  the  numbers  1,  2,  3,  4,  5,  6,  7,  and  8, 
and  half  each  quantity.  Treat  these  quantities  as 
feet,  which  set  up  from  the  base  C  A  on  A  B  to 
§■  inch  scale,  and  join  each  point  with  C.  The 
point  C  may  be  found  by  making  the  angle  E  B  G 
equal  to  20  degrees,  and  producing  B  6  to  C. 
This  is  what  is  called  a  sheer  diagram.  Half  sec- 
tions, if  necessary,  may  be  put  in  for  the  ends. 

Another  Way  of  Constructing  a  Sheer 
Diagram. — In  Fig.  15  let  0  denote  the  lowest  point 
of  the  sheer,  which  is  on  the  depth  moulded  line  C  A. 
Draw  perpendicular  0  P,  and  make  0  J  equal  to 
0  A,  and  erect  perpendiculars  J  K  and  A  B,  equal 
to  the  after  and  forward  sheer  respectively.  Join 
B  to  K  and  produce  it  to  C.  Divide  0  A  and 
0  J  into,  say,  8  equal  parts  in  the  points  1,  2,  3, 
4,  5,  6,  7.  Then  the  points  a,  b,  c,  d,  c,  /,  and  g  on 
0  P  will  be  found  in  the  following  manner  : — 

„        Ol2xOP„.     O  22  x  0  P    „       0  32xOP  A  ,     U  42  x  0  P 
0a  -'°/>=      OA2      '0c=      QA»      'O^-Og     ' 


OJ 


lO 


Oe 


OA2 

0  52  x  0  P 


n  ,    0  62  x  0  P       .  „       0  72  x  0  P 


OA2      '"J  OA2      >~"*v»  OA2 

Join  the  points  a,  b,  c,  d,  <>,/,  and  g  with  C,  producing  them  to 
A  B,  and  square  up  on  to  these  lines  their  corresponding  points  1,  2, 


3       4-        5       6        7       A 


Fig.  15. 


SHEER     DIAGRAM 


Cs> 


-  ,$ 


J       7        6        5       4        3        £        ) 


I         £         3       4-56         7       A 


LAYING -OFF  THE  SHEER  DRAUGHT. 


23 


3,  etc.,  as  shown,  then  the 
line  K  0  B  will  be  the  sheer 
contracted  in  the  length. 
It  can  be  lifted  on  to  the 
Sheer  in  Fig.  14  above  the 
depth  moulded,  by  taking 
the  distance  above  C  A  to 
each  of  the  points. 

It  will  be  readily  seen 
that  any  sheer,  to  any  scale, 
within  the  limits  of  the  dia- 
gram can  be  lifted  by  find- 
ing a  point  W  X,  between 
C  A  and  C  B,  square  to  C  A, 
which  is  equal  to  the  after 
sheer,  and  another  W1  X1 
equal  to  the  forward.  Then 
divide  WW1  into  16  equal 
parts,  and  produce  points 
square  to  C  A  until  they 
meet  their  corresponding 
inclined  lines  ■  then  the 
heights  lifted  and  set  off 
above  the  depth  moulded 
line  will  give  a  perfectly 
fair  line. 

Where  the  Lowest 
Point  is  not  on  the  Mid  = 
ship  Frame  or  midway 
between  the  Perpendi  = 
culars.  —  This,  in  some 
yards,  is  the  case,  then  the 
length  forward  beyond  the 
lowest  point  will  be  longer, 
say,  by  two  spaces  than  the 
after  distance.  Let  a  b  in 
Fig.  16  equal  forward,  and 
c  d  the  after  sheer,  divide 
ca  into  12  equal  parts,  let 
0  be  the  lowest  point ;  then 


*gp  lib/^ 


OF  THK 


UNIVERSITY 


LAYING-OFF  THE  SHEER  DRAUGHT. 


23 


3,  etc.,  as  shown,  then  the 
line  K  0  B  will  be  the  sheer 
contracted  in  the  length. 
It  can  be  lifted  on  to  the 
Sheer  in  Fig.  14  above  the 
depth  moulded,  by  taking 
the  distance  above  C  A  to 
each  of  the  points. 

It  will  be  readily  seen 
that  any  sheer,  to  any  scale, 
within  the  limits  of  the  dia- 
gram can  be  lifted  by  find- 
ing a  point  W  X,  between 
C  A  and  C  B,  square  to  C  A, 
winch  is  equal  to  the  after 
sheer,  and  another  W1  X1 
equal  to  the  forward.  Then 
divide  WW1  into  16  equal 
parts,  and  produce  points 
square  to  C  A  until  they 
meet  their  corresponding 
inclined  lines  •  then  the 
heights  lifted  and  set  off 
above  the  depth  moulded 
line  will  give  a  perfectly 
fair   line. 

Where  the  Lowest 
Point  is  not  on  the  Mid  = 
ship  Frame  or  midway 
between  the  Perpendi  = 
culars.  —  This,  in  some 
yards,  is  the  case,  then  the 
length  forward  beyond  the 
lowest  point  will  be  longer, 
say,  by  two  spaces  than  the 
after  distance.  Let  ab  in 
Fig.  16  equal  forward,  and 
c  d  the  after  sheer,  divide 
ca  into  12  equal  parts,  let 
0  be  the  lowest  point ;  then 


24 


NAVAL  ARCHITECTURE. 


the  after  length  0  c  will  be  divided  into  5,  and  0  a  into  7  equal 
parts.  Produce  the  points  to  meet  their  corresponding  lines,  the 
heights  of  which  set  off  above  depth  moulded  line  in  the  Sheer, 
which  gives  you  required  line. 

Another  Method  of  Sheer  Diagram  is  to  draw  a  quadrant  of 
a  circle,  H  J  K  in  Fig-.  16,  with  K  J  equal  to  the  greatest  sheer,  and 
divide  the  arc  H  J  into  8  equal  parts,  producing  the  points  1,  2,  3, 
etc.,  to  H  K,  as  shown.  Join  each  with  point  P,  found  in  the 
manner  already  described.  This  will  give  a  diagram  which  can  be 
used  in  the  same  manner  as  the  first. 


FigT-  17. 


Ready  Method  of  Finding  Sheer  Points,  which  is  easily 
done  and  of  considerable  use  on  small  scale  plans,  is  to  draw  a  semi- 
circle, ABC  in  Fig.  17,  to  a  suitable  scale  for  the  intended  plan, 
and  of  greater  radius  than  the  highest  sheer  point.  Then  find  a 
point  F  G  between  D  E  and  circle  line  taken  perpendicular  to  D  E 
and  equal  to  the  forward  sheer,  and  one  at  the  other  end  H  J  equal 
to  the  after  sheer.  If  the  distance  on  1)  E  between  JO  will  divide 
readily  into  equal  spaces,  do  so,  and  erect  perpendiculars  from  the 
points  to  the  circle  line  from  the  line  DE,  and  measure  off  inter- 
mediate sheer  points,  which  set  above  the  depth  moulded  line  in  the 
Sheer  plan.     If  J  G  does  not  divide  so,  then  produce  G  F  to  L  and 


CONTRACTED     LENQTH 


Fig.    IS. 
SHEER     DIAGRAM 


LAYING-OFP  THE  SHEER  DRAUGHT.  25 

H  J  to  K,  and  work  your  scale  diagonally  until  you  get  a  line  L  K 
which  divides  easily,  on  which  mark  divisional  points  and  produce 
them  perpendicular  to  D  E  as  shown.  Lift  the  heights  to  the  arc 
above  D  E  and  transfer  to  the  plan. 

Sheer  under  Freeboard  Tables. — In  the  regulations  for  free- 
board the  sheer  of  the  deck  at  the  side  is  defined  as  follows  : — "  At 
^  the  length  of  the  vessel  from  the  stem  or  stern  post  the  sheer  is  to 
be  55  per  cent,  of  the  sheer  at  stem  or  stern  post ;  at  \  the  length 
from  the  stem  or  stern  post  26  per  cent.,  and  at  §  the  length  7  per 
cent."    The  sheer  diagram,  Fig.  18,  has  been  prepared  to  set  off  these 
percentages  without  the  trouble  of  calculating.     As  an  example,  let 
0  D,  to  scale,  equal  forward  sheer  on  the  stem,  and  A  B  after  sheer  on 
the   stern  post.     Then    the   intermediate   heights   above   the  depth 
moulded  line  in  Fig.  19  are  lifted  from  the  base  E  F  in  Fig.   18; 
that  is,  0  D  set  up  on  the  stem,  C  a  at  ^,  C  b  at  £,  C  c  at  §,  the  half 
length  being  the  touching  point.     Similarly,  A  B  is  the  after  sheer  on 
the  stern  post,  and  the  intermediates  A  a1  at  |,  A  b1  at  },  A  c1  at  | 
from  the  after  end.     By  this  means  a  sufficient  number  of  spots  are 
got  for  drawing  in  the  line  shown  contracted  in  the  length  in  the  Fig. 
19.     These  divisions  in  the  length  are  shown  further  subdivided  to 
TJg-  of  the  length,  to  secure  fairness  where  there  is  much  spread.     Any 
scale  may  be  used  on  this  diagram  :  and  if  necessary  the  radiating  lines 
may  be  produced  to  suit  1  inch  scale  in  "  laying  off  "  a  very  long  vessel. 
The  System  of  Laying = off  in  vogue  at  the  large  establishment 
of  Messrs.  C.  S.  Swan  &  Hunter,  Limited,  Wallsend-on-Tyne,  is 
interesting  as  a  novel  and  successful  attempt  to  overcome  some  of  the 
practical  difficulties  involved  in  laying-off  on  drawing  paper.     It  is 
given  here  because  it  is  an  entirely  new  departure,  and  as  far  as  the 
main  ideas  for  its  "raison  d'etre"  are  concerned  it  is  a  decided  success. 
Some  trouble  having  been  experienced  in  the  laying-off  department 
of  this  and  other  firms,  owing  to  the  gradual  shrinkage  of  the  paper 
causing  slight  inaccuracies  in  the  subsequent  readings  taken  from  it, 
Mr.   G-.  B.  Hunter,  chairman  of  this  company,  decided  to  try  the 
experiment  of  laying-off  on  some  material  which  should  be  incapable 
of  shrinkage.     The  use  of  wood  tables  for  laying-off  was  not  found  to 
be  perfectly  satisfactory  and  accurate,  and  Mr.  Hunter  finally  decided 
to  try  the  respective  merits  of  white  marble,  white  cast  glass  and 
opal.     The  principal  table  for  laying-off  on  1  inch  scale  is  composed 
of  white  marble  slabs  fitted  in  lengths  of  about  6  feet,  carefully  jointed, 
with  a  total  length  of  30  feet.     On  this  table  the  Sheer  and  the 


OF   THE 


UNIVERSITY 


LAYING-OFP  THE  SHEER  DRAUGHT.  25 

H  J  to  K,  and  work  your  scale  diagonally  until  you  get  a  line  L  K 
which  divides  easily,  on  which  mark  divisional  points  and  produce 
them  perpendicular  to  D  E  as  shown.  Lift  the  heights  to  the  arc 
above  D  E  and  transfer  to  the  plan. 

Sheer  under  Freeboard  Tables. — In  the  regulations  for  free- 
board the  sheer  of  the  deck  at  the  side  is  defined  as  follows  : — "  At 
^  the  length  of  the  vessel  from  the  stem  or  stern  post  the  sheer  is  to 
be  55  per  cent,  of  the  sheer  at  stem  or  stern  post ;  at  £  the  length 
from  the  stem  or  stern  post  26  per  cent.,  and  at  §  the  length  7  per 
cent."  The  sheer  diagram,  Fig.  18,  has  been  prepared  to  set  off  these 
percentages  without  the  trouble  of  calculating.  As  an  example,  let 
C  D,  to  scale,  equal  forward  sheer  on  the  stem,  and  A  B  after  sheer  on 
the  stern  post.  Then  the  intermediate  heights  above  the  depth 
moulded  line  in  Fig.  19  are  lifted  from  the  base  E  F  in  Fig.  18; 
that  is,  C  D  set  up  on  the  stem,  C  a  at  §-,  C  b  at  \,  C  c  at  §,  the  half 
length  being  the  touching  point.  Similarly,  A  B  is  the  after  sheer  on 
the  stern  post,  and  the  intermediates  A  a1  at  £,  A  b1  at  \,  A  rl  at  § 
from  the  after  end.  By  this  means  a  sufficient  number  of  spots  are 
got  for  drawing  in  the  line  shown  contracted  in  the  length  in  the  Fig. 
19.  These  divisions  in  the  length  are  shown  further  subdivided  to 
yV  of  the  length,  to  secure  fairness  where  there  is  much  spread.  Any 
scale  may  be  used  on  this  diagram  :  and  if  necessary  the  radiating  lines 
may  be  produced  to  suit  1  inch  scale  in  "  laying  off  "  a  very  long  vessel. 

The  System  of  Laying=off  in  vogue  at  the  large  establishment 
of  Messrs.  0.  S.  Swan  &  Hunter,  Limited,  Wallsend-on-Tyne,  is 
interesting  as  a  novel  and  successful  attempt  to  overcome  some  of  the 
practical  difficulties  involved  in  laying-off  on  drawing  paper.  It  is 
given  here  because  it  is  an  entirely  new  departure,  and  as  far  as  the 
main  ideas  for  its  "raison  d'etre'1  are  concerned  it  is  a  decided  success. 

Some  trouble  having  been  experienced  in  the  laying-off  department 
of  this  and  other  firms,  owing  to  the  gradual  shrinkage  of  the  paper 
causing  slight  inaccuracies  in  the  subsequent  readings  taken  from  it, 
Mr.  G-.  B.  Hunter,  chairman  of  this  company,  decided  to  try  the 
experiment  of  laying-off  on  some  material  which  should  be  incapable 
of  shrinkage.  The  use  of  wood  tables  for  laying-off  was  not  found  to 
be  perfectly  satisfactory  and  accurate,  and  Mr.  Hunter  finally  decided 
to  try  the  respective  merits  of  white  marble,  white  cast  glass  and 
opal.  The  principal  table  for  laying-off  on  1  inch  scale  is  composed 
of  white  marble  slabs  fitted  in  lengths  of  about  G  feet,  carefully  jointed, 
with  a  total  length  of  30  feet.     On  this  table  the  Sheer  and  the 


26  NAVAL  ARCHITECTURE. 

Half  Breadth  plans  are  drawn.  The  other  two  tables — one  of  cast 
glass  and  one  of  opal — are  used  for  the  fore  and  after  Body  sections 
respectively.  It  may  be  mentioned  that  the  draughtsman  in  charge 
of  the  work  prefers  the  white  marble  to  either  of  the  other  tables,  as 
he  finds  that  the  glossy  surface  on  the  cast  glass  and  opal  is  against 
quick  working  with  a  drawing  pen,  and  in  cold  weather  the  moisture 
from  the  hands  condenses  more  rapidly  on  these  than  on  the  marble. 

The  laying-off  is  done  to  a  scale  of  1  inch  to  the  foot.  The 
system  adopted  is  briefly  as  follows  : — The  level  lines  and  frames 
having  been  marked  off  on  the  Sheer  slab,  the  sheer  and  half  breadth 
of  the  rail  are  faired  by  contraction  and  drawn  in.  They  are  then 
transferred  to  the  section  slab,  thus  giving  the  correct  sheer  and  half 
breadth  at  the  top  of  each  frame  station.  The  water  lines  are  now 
roughed  in  on  the  Half  Breadth  and  the  buttocks  faired  to  them  in 
the  Sheer.  Then  the  buttock  and  water  line  spots  are  transferred 
on  to  the  section  table  and  the  cross  sections  drawn  in.  Corrections 
are  here  made  until  the  buttock,  water  line,  and  section  spots  all  agree 
in  absolute  fairness.  When  this  stage  has  been  arrived  at  diagonals 
are  drawn  in  on  the  Body  section  table  in  convenient  positions,  as 
square  to  the  frames  as  practicable.  These  diagonals  are  then  lifted 
off  and  run  on  the  Sheer  slab  to  further  fair-up  the  sections.  The 
midship  portions  of  the  water  lines  and  buttocks  are  next  faired  by 
contraction.  The  work  up  to  this  stage  has  been  done  in  pencil,  but 
now  the  corrected  lines  are  inked  in.  The  off -sets  are  now  lifted  off 
and  transferred  to  the  loft  book  for  scrieving  and  future  reference. 
The  slabs  are  easily  cleaned  with  Monkey  Brand  Soap,  and  are 
then  ready  for  fresh  work. 


CANT    FRAMES.  27 


CHAPTER  II. 

Cant  Frames  in  the  Fore  Body :  Projection  into  the  Sheer — True  Form  in  the 
Sheer — Projection  into  the  Body— Projection  into  the  Sheer  on  Diagonal 
Lines — Expansion  in  the  Sheer  on  Diagonal  Lines— Expansion  of  the 
Bevelled  Edge — Projection  into  the  Sheer  on  Bow  Lines— Expansion  of 
Moulded  Edge  on  Bow  Lines.  Stern  Cant  Frames :  Projection  of  the 
Moulded  Edge  into  the  Sheer — Projection  of  the  Bevelled  Edge  into  the 
Sheer — True  Form  of  the  Moulded  Edge  in  the  Sheer — True  Form  of  the 
Bevelled  Edge— Lifting  Bevels — Moulds. 


CANT   FEAMES. 

Cant  Frames. — These  are  always  fitted  abaft  of  the  transom, 
and  in  barges  and  very  full  ships  are  invariably  fitted  at  both  ends. 
By  cant  frames  is  meant  those  which  are  not  square  to  the  centre  line 
of  the  vessel. 

Cant  Frames  in  the  Fore  Body. — In  Fig.  20  place  the  heel  or 
moulded  edge,  A  E,  of  the  frame  in  the  Half  Breadth  as  square  as 
possible  to  the  level  lines.  Set  off  the  bevelled  edge  G  L  by  girthing 
from  the  moulded  edge  the  width  of  the  frame  flange  on  the  level 
lines  and  rail.  Put  a  curve  through  the  spots  ;  and  show  on  the  half 
siding  of  the  keel  M  N.  It  may  be  noted  that  the  bosom  of  these 
frames  look  towards  the  centre  line  of  the  vessel  to  give  open  bevel. 

Projection  into  the  Sheer. — Square  up  the  point  B  on  to  the 
top  of  the  keel,  C  and  D  to  their  corresponding  level  lines,  and  E 
to  the  rail.  Do  the  same  with  the  bevelled  edge,  H1  being  the 
termination  on  the  top  of  the  keel  squared  up  from  the  point  H,  and 
L1  on  the  rail.  Run  lines  through  the  spots  for  each  edge,  which 
shows  the  frame  in  its  true  position. 

True  Form  in  the  Sheer. — Draw  the  level  lines  E1  E2  and  L1  L2 
through  the  points  E1  and  L1,  the  terminations  of  the  moulded  and 
bevelled  edges  on  the  rail.  Lift  the  intersections  of  the  moulded  edge 
in  the  Half  Breadth  with  the  half  siding  of  the  keel,  level  lines,  and 
rail,  by  placing  a  batten  on  the  run  of  the  line  and  marking  on  it  the 
centre  A,  half  siding  B,  and  points  C,  D,  and  E.  Set  these  out  in  the 
Sheer  on  their  respective  lines  from  the  perpendicular  A1  P.  That  for 
the  rail,  A  E,  set  off  from  F,  F  E2,  and  A  B  on  the  top  of  the  keel 
from  A1  F.     Do  the  same  with  the  bevelled  edge,  taking  care  to  lift 


28 


NAVAL   AltCHITECTUKE. 


from  the  line  A  G,  which  is  square  to  A.  E  at  the  centre  ;  G  H  is  the 
distance  for  the  bevelled  edge  on  the  top  of  the  keel  in  the  Sheer,  and 
G  L  that  for  the  rail  on  the  level  line  F  L2.  Run  lines  through 
the  spots,  dotting  the  bevelled  edge  for  distinction.  The  bevel  on 
the  bar  at  any  point  is  the  distance   between  the   expanded   edges 


Fig.   20. 


BODY 


SHEER 


taken  square  to  the  moulded  line.  B2,  C2,  D2,  and  E'-'  is  the  true  form 
of  the  moulded  edge,  to  which  the  frame  must  be  turned.  Wood 
moulds  may  be  made  giving  the  shape  of  each  frame,  with  the  position 
of  the  plate  edges,  keelsons,  decks,  and  ribbands,  accompanied  by  a 
bevelling-board  showing  the  bevel  at  the  plate  edges;  or  the  true  form 
may  be  scrieved  in  on  the  scrieve-board,  with  the  true  position  of  the 
ribbands,  etc.,  marked  on  the  scrieves. 


CANT   FRAMES. 


29 


Projection  into  the  Body.— Square  over  into  the  Body  the  points 
B1  and  E1  for  the  terminations,  and  set  off  on  A2  B2  the  half  siding, 
A2  B3,  of  the  keel  at  B,  then  lift  off  from  the  Half  Breadth,  square 
to  the  centre  line,  the  intersections  of  the  moulded  edge  of  the  cant 
with  the  level  lines  and  rail,  transferring  them  on  to  their  respective 


BODY 


Fig.  21. 


SHEER 


level  lines  in  the  Body.  Pass  the  curve  B3  and  E3  through  the  spots 
which  will  give  the  required  line.  The  bevelled  edge  is  projected  in 
the  same  way ;  of  course,  the  cutting  point  on  the  rail  will  be  slightly 
higher.  The  cants  may  not  extend  to  the  rail,  but  it  will  be  evident 
that  the  rail  sheer  is  only  chosen  to  represent  any  sheered  Hue. 

It  is  sometimes  necessary  to  find  the  cutting  points  of  diagonals, 
bow  lines,  and  ribbands  on  the  projected  and  expanded  edges  of  the 


30  NAVAL   AECHITECTURE. 

cants  in  the  Sheer.  Fig.  21  is,  therefore,  given,  showing  in  one  sketch 
the  diagonals,  level  lines,  ribbands,  and  bow  lines,  in  conjunction  with 
the  forward  cants.  With  a  pair  of  compasses  and  the  trace  lines,  the 
method  of  cutting  may  be  easily  understood,  but  to  make  the  matter 
perfectly  clear  it  will  be  explained  in  detail.  The  ship  is  faired-up 
on  square  stations  before  the  cants  are  placed  in  position.  Let  it  be 
so  in  the  examples  we  are  considering. 

Projection  of  the  Cants  into  the  Sheer  on  Diagonal 
Lines. — Show,  in  Fig.  22,  the  half  siding  of  the  keel  and  stem  LM 
and  L1  M1  in  the  Half  Breadth  and  Body.  Then  trace  diagonals 
in  the  first  plan,  on  the  ordinary  square  frames,  by  lifting  the  cutting 
points  square  to  the  centre  of  the  Body  and  transferring.  Their 
terminations  will  be  got  by  squaring  the  intersection  points  on  L1  M1 
over  to  the  inside  of  the  stem  in  the  Sheer,  and  dropping  the 
points  on  to  the  half  siding  L  M  of  the  Half  Breadth.  Draw  the 
cants  1,  2,  and  3  in  position  in  the  Half  Breadth,  after  which  they 
are  placed  in  the  Body  by  lifting  the  cutting  points  g,  //,  /-,  /,  m,  n, 
and  0  on  each  cant,  square  out  from  the  centre  line,  and  transferring 
them  in  the  same  manner  on  to  the  diagonal  lines.  The  termination 
at  the  foot  is  found  by  projecting  p  on  to  the  top  of  the  keel  p2,  and 
from  there  into  the  Body  on  L1  M1.  The  other  cants  are  lifted  into 
the  Body  in  the  same  way.  Then  square  into  the  Sheer  the  points 
/),//,  J/,  k,  1,  m,  n,  and  0,  and  produce  from  the  Body  the  corresponding- 
points  p1ig\  h\  h\  and  so  on,  until  they  meet,  which  will  give  cutting 
points  //2,  //2,  //2,  Z"2,  etc.,  for  No.  3  cant,  and  also  for  projections  of 
the  diagonals.  If  this  is  done  with  2  and  3  cants,  the  diagonals  and 
cants  can  be  drawn  in  their  true  positions  by  tracing  lines  through 
the  spots  as  shown.  The  bevelled  edge  may  be  produced  in  the  same 
manner. 

Expansion  of  the  Cants  in  the  Sheer  on  Diagonal 
Lines. — To  make  it  clear  only  one  cant,  Xo.  3,  will  be  taken.  In 
Fig.  22  produce  level  lines  through  the  points  <r,  n?,  m2,  etc.,  in- 
definitely.    Draw  up  perpendicular  A   B  from  A.     Then  lift  on  the 

run  of  the  cant  the  distances  A;;,  A  //,  A  //,  A  /-,  A  / A  0, 

and  place  them  on  their  corresponding  level  heights  in  the  Sheer 
forward  of  A  B,  and  draw  line  through  the  spots,  which  will  give 
true  moulded  form  of  the  cant  No.  3.  Ao  is  set  off  on  B^2  produced, 
and  A  p  on  the  top  of  the  keel  produced  from  p2. 

Expansion  of  the  Bevelled  Edge  on  Sheer  Diagonal 
Lines. — Draw  A  A1  square  to  A  0  from  A.     Then  lift  intersections 


FORWARD    CAN 


BODY 


Fig.  22. 


SHEER 


FORWARD    CANTS 


CANT    FEAMES. 


31 


of  half  siding,  etc.,  from  A1  on  the  line  of  the  bevelled  edge,  and 
transfer  into  the  Sheer  on  their  level  heights  from  AB,  passing  a 
curve  through  the  spots,  which  will  give  the  line  of  the  bevelled  edge. 
It  is  usual  to  place  the  true  form  of  the  cants  forward  on  the 
scrieve-board  with  the  position  of  ribbands,  decks,  plate  edges,  and 


BODY 


Fig.    23. 


SHEER 


keelsons  marked  upon  them.     Sometimes  a  wood  mould  is  made  of 
each  with  the  different  markings  on  and  a  line  for  the  foot. 

Projection    of   the    Cants    into    the    Sheer    on    the    Bow 
Lines. — Show  cants  in  the  Half  Breadth  and  the  Body  of  Fig.  23  in 

the  manner  already  described.     Square  up  the  points  a,  b,  c,  d,  and  e, 
until  they  meet  in  a\  b1,  c\  rf\  and  e\  the  corresponding  points  a2,  b2, 


fpLiBR^J 


or  the 


UNIVERSITY 


CANT    FRAMES. 


31 


of  half  siding,  etc.,  from  A1  on  the  line  of  the  bevelled  edge,  and 
transfer  into  the  Sheer  on  their  level  heights  from  AB,  passing  a 
curve  through  the  spots,  which  will  give  the  line  of  the  bevelled  edge. 
It  is  usual  to  place  the  true  form  of  the  cants  forward  on  the 
scrieve-board  with  the  position  of  ribbands,  decks,  plate  edges,  and 


BODY 


Fig.    23. 


SHEER 


HAL^F  ;BREADTf| 

i  I 
I   'I    ■ 


keelsons  marked  upon  them.     Sometimes  a  wood  mould  is  made  of 
each  with  the  different  markings  on  and  a  line  for  the  foot. 

Projection  of  the  Cants  into  the  Sheer  on  the  Bow 
Lines. — Show  cants  in  the  Half  Breadth  and  the  Body  of  Fig.  23  in 
the  manner  already  described.  Square  up  the  points  a,  1>,  c,  d,  and  e, 
until  they  meet  in  a1,  h\  c\  d\  and  e\  the  corresponding  points  a2,  lr, 


?y'l  NAVAL    ARCHITECTURE. 


r2,  d2,  and  e2,  produced  from  the  Body,  by  which  No.  3  cant  may  be 
drawn  in.  Repeat  the  process  for  cants  1  and  2,  and  the  traces  of  all 
the  bow  lines  and  cants  may  be  produced. 

Expanded  Moulded  Edge  on  the  Bow  Lines. — Produce 
level  lines  in  the  Sheer  through  points  a1,  bl,  c1,  d\  and  e1,  and  set  off 
on  them  from  A  B  the  distances  A  a,  A  h,  A  c,  A  d,  and  A  e  on  their 
corresponding  level  heights.  A  curve  passed  through  the  spots  shows 
the  true  form  of  No.  3  cant. 

The  bevelled  edge  may  be  lifted  in  the  same  way  only  along  A1  p 
from  A1,  and  set  off  on  the  level  heights  of  the  intersection  of  the 
edge  with  the  bow  lines  in  the  Sheer.  The  manner  of  terminating  at 
foot  and  rail  has  been  already  indicated. 

The  Stern  Cant  Frames. — After  the  completion  of  the  fairing 
process  of  the  stern  by  buttocks  and  level  lines,  the  cants  are  arranged 
around  the  knuckle  line  in  the  Half  Breadth,  from  the  transom  on  one 
side  to  the  corresponding  point  on  the  other,  the  spacing  being  the 
same  as  the  ordinary  framing  of  the  square  stations.  Through  these 
points,  on  the  knuckle,  they  are  drawn  as  near  as  practicable  square  to 
the  rail,  knuckle  and  deck  lines,  to  give  the  best  support  to  the  stern 
plating.  Begin  by  striking  in  position  the  moulded  edge  of  the  cants, 
that  is  the  heel  of  the  bar  shown  in  the  Half  Breadth  of  Fig.  24,  and 
parallel  to  it  show  the  bevelled  edge.  It  may  be  noted  that  the 
bosom  of  the  cants  at  each  side  of  the  vessel  look  towards  the  centre 
line  to  give  open  bevel. 

Projection  of  the  Moulded  Edge  into  the  Sheer. — Square 
up  from  the  Half  Breadth  the  intersection  of  the  moulded  edge  at  a, 
b,  r,  and  d  on  to  their  corresponding  lines  in  the  Sheer  a1,  b\  c\  and 
d1.  The  head  of  the  cant  will  terminate  on  the  rail  at  side,  d1,  and 
the  foot  of  the  transom  will  be  found  by  lifting  the  distance  T  e  in  the 
Half  Breadth,  and  setting  it  out  on  the  transom  in  the  Body,  square 
to  the  centre,  marked  e1,  and  then  levelling  the  point  over  into  the 
Sheer  on  to  the  transom  station,  <-2,  as  shown  by  trace  lines.  A  curve 
is  then  passed  through  the  points.  It  will  not  lie  a  continuous  fair 
curve,  for  a  distinct  knuckle  is  made  at  b1.  This  process  is  repeated 
until  all  the  cants  are  shown  in  their  true  position  in  the  Sheer. 

Projection  of  the  Bevelled  Edge  into  the  Sheer. — Square 
points  //,  //,  /,  and  /  on  to  their  corresponding  lines  in  the  Sheer,  and 
transfer  T  /'into  the  Body,  as  in  the  moulded  edge,  and  square  over/1 
to/2,  which  gives  termination  of  the  bevelled  edge  on  the  transom. 

True  Form  of  the  Moulded  Edge  in  the  Sheer. — Of  course 
the  cants,  for  the  purpose  of  turning  into  their  proper  shape,  have  to 


EXPANSION     OF    CANTS 


BODY 


EXPAN5ION     OF    CANTS 


CANT  FRAMES.  33 

be  expanded  in  their  true  form.  Place  level  lines  through  the  projected 
points  &1  and  d1  on  the  knuckle  and  rail.  Then  lay  a  batten  on  the 
moulded  edge  of  No.  6  cant,  and  lift  the  distances  a,  i,  c,  and  d,  from 
e,  and  set  them  out  in  the  Sheer,  from  the  transom,  on  their  corre- 
sponding heights  or  level  lines.  Through  the  spots  in  Fig-.  24  is  drawn 
deep  lines,  which  is  the  expanded  form  of  the  moulded  edge  of  each  cant. 

True  Form  of  tlie  Bevelled  Edge  in  the  Sheer. — Make  e  n 
square  to  the  moulded  edge  at  the  point  e,  and  lift  from  n  on  the 
bevelled  edge  g,  h,  J:;  and  /,  and  set  them  out  from  the  transom  in  the 
Sheer  on  their  corresponding  heights.  The  foot  is  /2,  and  the  head 
will  be  got  by  drawing  a  level  line  through  the  intersection  of  the 
point  /,  squared  on  to  the  rail  in  the  Sheer.  Curves  are  traced  through 
the  spots.     These  lines  are  shown  dotted  for  distinction. 

In  this  way  all  the  cants  are  indicated  in  their  true  form  in  the 
Sheer,  or  they  may  be  drawn  on  the  loft  floor  clear  of  the  stern 
as  shown.  In  many  cases  these  cants  are  only  fitted  to  the  line  of 
the  deck,  so  that  may  be  the  sheer  height  instead  of  the  rail. 

Lifting  the  Bevels. — The  amount  of  bevel  is  the  difference 
between  the  expanded  moulded  and  bevelled  edges  taken  square  to  the 
moulded  edge.  Where  the  bevelled  edge  lies  outside  of  the  moulded 
edge  it  is  "open,"  and  when  inside  it  is  "close."  These  bevels  are 
lifted  at  the  foot,  knuckle,  rail,  and  sometimes  intermediate  points. 
They  are  given  to  the  frame-turner  on  a  piece  of  pine  board  the 
width  of  the  shell  flange.  The  bevels  of  the  feet  are  also  given  for 
cutting  the  flanges  to  fit  transom  floor.  The  shell  flange  of  No.  6 
cant  should  be  cut  to  a,  e,f,  seen  in  the  Half  Breadth,  and  the  other 
flange  should  be  cut  to  b1,  e2,  p. 

It  may  be  noted  that  the  bevel  at  the  foot  of  each  cant  would  be 
more  correctly  taken  if  the  distance  e  n,  the  width  of  the  bar,  was  set 
out  level  from  e1  in  sketch  W,  and  produced  parallel  to  the  centre  line 
to  cut  T  frame  ;  and  the  point  n1  lifted  on  to  the  transom  in  the  expan- 
sion in  each  case,  instead  of  p,  for  the  termination  of  the  bevelled 
edge.  This  may  be  understood  more  clearly  by  swinging  the  cant  b 
on  the  point  e,  until  ed~  is  square  to  the  transom  frame,  then  n  will 
be  on  the  line  eT. 

Moulds. — A  wood  template  is  made  of  the  expanded  moulded 
edge  of  each  cant,  having  marked  on  it  the  vertical  position  of  the 
transom,  and  the  position  of  the  rail  or  deck,  and  hatpin,  if  any. 
Where  a  harpin  is  fitted  a  hole  should  be  punched  in  each  cant  for 
attachment.    The  points  where  the  bevels  are  taken  are  also  indicated. 

4 


OF   THF 


UNIVERSITY 


CANT  FRAMES.  33 

be  expanded  in  their  true  form.  Place  level  lines  through  the  projected 
points  bl  and  d1  on  the  knuckle  and  rail.  Then  lay  a  batten  on  the 
moulded  edge  of  No.  6  cant,  and  lift  the  distances  a,  b,  c,  and  d,  from 
e,  and  set  them  out  in  the  Sheer,  from  the  transom,  on  their  corre- 
sponding heights  or  level  lines.  Through  the  spots  in  Fig.  24  is  drawn 
deep  lines,  which  is  the  expanded  form  of  the  moulded  edge  of  each  cant. 

True  Form  of  the  Bevelled  Edge  in  the  Sheer. — Make  e  n 
square  to  the  moulded  edge  at  the  point  e,  and  lift  from  /?  on  the 
bevelled  edge  g,  h,  h,  and  /,  and  set  them  out  from  the  transom  in  the 
Sheer  on  their  corresponding  heights.  The  foot  is  f2,  and  the  head 
will  be  got  by  drawing  a  level  line  through  the  intersection  of  the 
point  /,  squared  on  to  the  rail  in  the  Sheer.  Curves  are  traced  through 
the  spots.     These  lines  are  shown  dotted  for  distinction. 

In  this  way  all  the  cants  are  indicated  in  their  true  form  in  the 
Sheer,  or  they  may  be  drawn  on  the  loft  floor  clear  of  the  stern 
as  shown.  In  many  cases  these  cants  are  only  fitted  to  the  line  of 
the  deck,  so  that  may  be  the  sheer  height  instead  of  the  rail. 

Lifting  the  Bevels. — The  amount  of  bevel  is  the  difference 
between  the  expanded  moulded  and  bevelled  edges  taken  square  to  the 
moulded  edge.  Where  the  bevelled  edge  lies  outside  of  the  moulded 
edge  it  is  "open,"  and  when  inside  it  is  "close."  These  bevels  are 
lifted  at  the  foot,  knuckle,  rail,  and  sometimes  intermediate  points. 
They  are  given  to  the  frame-turner  on  a  piece  of  pine  board  the 
width  of  the  shell  flange.  The  bevels  of  the  feet  are  also  given  for 
cutting  the  flanges  to  fit  transom  floor.  The  shell  flange  of  No.  6 
cant  should  be  cut  to  a,  e,f,  seen  in  the  Half  Breadth,  and  the  other 
flange  should  be  cut  to  J1,  e2,  p. 

It  may  be  noted  that  the  bevel  at  the  foot  of  each  cant  would  be 
more  correctly  taken  if  the  distance  e  n,  the  width  of  the  bar,  was  set 
out  level  from  e1  in  sketch  W,  and  produced  parallel  to  the  centre  line 
to  cut  T  frame  ;  and  the  point  n1  lifted  on  to  the  transom  in  the  expan- 
sion in  each  case,  instead  of  f2,  for  the  termination  of  the  bevelled 
edge.  This  may  be  understood  more  clearly  by  swinging  the  cant  h 
on  the  point  e,  until  ed2  is  square  to  the  transom  frame,  then  n  will 
be  on  the  line  eT. 

Moulds. — A  wood  template  is  made  of  the  expanded  moulded 
edge  of  each  cant,  having  marked  on  it  the  vertical  position  of  the 
transom,  and  the  position  of  the  rail  or  deck,  and  harpin,  if  any. 
Where  a  harpin  is  fitted  a  hole  should  be  punched  in  each  cant  for 
attachment.    The  points  where  the  bevels  are  taken  are  also  indicated. 

4 


34  NAVAL  ARCHITECTURE. 


CHAPTER  TIL 

Be;im  Camber  Allowed — Method  of  Laying  it  off — To  Draw  in  the  Deck  at 
Side  Line— Expansion  of  the  Deck  Surface— Method  of  Laying-off 
Tapered  Stringer  Plate — Deck  Plate  Edges— Wide  Stringer  Plates. 


DECKS. 

Beam  Camber. — The  beams  of  the  upper  decks  of  merchant 
ships  are  rounded  a  quarter  of  an  inch  for  every  foot  in  the  length  of 
the  beam  ;  that  is,  a  ship  40  feet  wide  on  the  midship  frame  measured 
level  across  from  the  deck  at  one  side  to  deck  at  the  other  side  must 
not  have  less  than  10  inches  "camber,"  or  "round  up,"  at  the  centre 
line  above  the  level  line  joining  the  side  line  points.  This  camber  is 
gradually  reduced  towards  the  ends,  as  the  beam  of  the  ship  decreases. 
All  the  beams  take  the  form  of  the  midship  camber,  so  that  the  deck 
surface  is  a  fair  plane.  The  other  decks  when  laid  follow  the  same 
rule.  Lower  deck  beams,  when  no  covering  is  put  upon  them,  are 
ordinarily  made  level.  There  are  several  methods  adopted  for  finding 
the  camber  curve. 

First  Method  of  Laying  =  off  the  Camber.— In  Fig.  25,  let 
A  B  equal  the  Half  Breadth  of  the  ship  at  the  deck  on  the  midship 
frame.  Set  up  perpendicular  B  B1  equal  to  the  required  camber. 
Join  B1  to  A,  and  erect  A  A1  perpendicular  to  A  B1  at  the  point  A. 
Produce  B1  to  A1  parallel  to  B  A.  Divide  B1  A1  into  a  suitable 
number  of  equal  spaces,  say  four,  A1  E1,  E1  F1,  F1  G1,  G1  B1.  Divide 
A  B  into  the  same  number  of  equal  spaces,  A  E,  E  F,  F  G,  and  G  B. 
Join  E  and  E\  F  and  F1,  G  and  G1.  Erect  A  L  perpendicular  to  A  B. 
Divide  A  L  into  the  same  number  of  equal  spaces  as  A  B.  Join  M, 
N  and  0  to  B1.  Then  the  cutting  points  of  A1  B1  and  B  B1,  M  B1, 
and  GG1,  NB1  and  F  F1,  OB1  and  E  E1,  BA  and  A  A1,  give  5 
spots  for  drawing  in  the  curve.  Repeat  process  on  the  other  side  of 
the  centre  line  and  you  will  secure  curve  for  the  entire  beam. 

Second  Method.— In  Fig-.  26,  let  AB  equal  the  length  of  the 
beam  and  C  the  centre  line.  Erect  C  D  perpendicular  to  A  B  and 
equal  to  twice  the  camber.  Join  D  to  A  and  B.  From  D  on  D  B 
set  off  equal  distances,  say,  one  foot  apart.  Do  the  same  with  D  A. 
Number  each  one,  beginning  as  shown  in  the  sketch,  and  join  1  to  1, 
2  to  2,  and  so  on.  It  will  be  seen  that  these  lines  form  the  curve 
themselves,  or  the  cutting  points  are  a,  b,  c,  d,  e,  etc. 


CAMBER     FORM. 
FIQ    25. 


DECKS.  35 

Third  Method.— In  Fig.  27,  draw  AB  perpendicular  to  A  D 
from  A.  Describe  from  A  a  quadrant  of  a  circle  with  A  C  equal  to 
the  midship  camber.  Divide  A  C  into,  say,  four  equal  parts  by  the 
points  a,  b,  d,  and  the  arc  B  C  into  the  same  number  of  equal  parts 
by  e,  f,  //,  and  join  a  to  r,  b  to/,  and  d  to  //.  A  D  equals  half  beam, 
divide  it  into  four  equal  parts  in  the  points  E,  F,  and  G.  Erect 
perpendiculars  E  E1  =  a  e,  FF'  =  b  f,  and  G  G1  =  dg.  Draw  curve 
through  the  points  B,  E1,  F1,  G1  and  D.  Repeat  process  for  the 
opposite  side  A  D:,  then  you  have  form  of  full  beam. 

Fourth  Method. — In  Fig.  28,  let  A  B=half  beam,  A  C=camber. 
Describe  A  C  K  with  radius  A  C.  Divide  A  K  and  C  K  into  equal 
parts  and  A  B  into  the  same  number  of  equal  parts  as  A  K,  and  erect 
perpendiculars.  Produce  d  to  meet  E  D,  e  to  meet  G  F,  /  to  meet 
J  H.  Pass  a  curve  through  the  cutting  points,  repeat  for  the  other 
side  A  B1,  and  you  have  an  approximate  method,  which  is  occasionally 
used. 

To  Draw  in  the  Deck  at  Side  Line, — Run  in  the  Sheer  the 
deck  at  the  centre,  and  lift  from  the  Half  Breadth  the  half  ordinates 
of  the  deck  at  about  every  fifth  frame.  Set  these  points  a,  b,  c,  d,  e, 
and  /  out  square  on  each  side  of  the  centre  A  B  in  Fig.  29 — die 
camber  curve.  Stretch  a  line  across  from  point  to  point,  a  to  a1,  b  to 
h\  and  so  on,  and  measure  the  amount  of  camber  due  to  the  width, 
Br/2  for  section  a  a1,  B  b2  for  bP,  etc.,  and  place  these  distances 
below  the  deck  at  the  centre,  which  are  points  for  the  curve  of  side. 
Forward  the  line  should  terminate  on  the  inside  of  the  stem,  aft 
usually  on  the  centre.  At  the  extreme  ends,  owing  to  the  rapid 
reduction  of  widths,  this  line  will  take  a  sudden  rise  to  the  centre  line. 

Expansion  of  the  Deck  Surface. — Girth  in  the  Sheer  the 
deck  line  at  centre  for  the  position  of  the  frame  stations,  stem  and 
stern  points.  Lay  the  batten  on  a  straight  line  and  mark  frame 
stations,  etc.,  from  which  erect  perpendiculars.  Set  out  square  to 
the  centre  on  the  camber  curve  the  half  beam  at  each  section,  and 
girth  the  distances  of  these  points  around  the  curve  relative  to 
the  middle  line.  Place  the  girths  on  their  respective  perpendiculars 
in  the  expansion,  and  draw  curve  through  the  spots.  Repeat  the 
curve  for  the  other  side,  then  the  enclosed  space  is  a  near  approx- 
imation to  the  deck  area,  which  may  be  calculated  by  Simpson's 
Pailes  and  the  open  or  uncovered  spaces  deducted. 

To  Show  a  Tapered  Side  Stringer  Plate  on  the  Deck 
Plan, — In  Fig.  30,  draw  in  position  the  frames  1,  2,  3,  4,  and  5,  and 


\V&  libr^ 


OF  THE 


UNIVERSITY 


DECKS.  35 

Third  Method. — In  Fig.  27,  draw  AB  perpendicular  to  A  D 
from  A.  Describe  from  A  a  quadrant  of  a  circle  with  A  C  equal  to 
the  midship  camber.  Divide  A  C  into,  say,  four  equal  parts  by  the 
points  a,  b,  d,  and  the  arc  B  C  into  the  same  number  of  equal  parts 
by  p,  f,  //,  and  join  a  to  c,  b  to/,  and  d  to  //.  A  D  equals  half  beam, 
divide  it  into  four  equal  parts  in  the  points  E,  F,  and  G.  Erect 
perpendiculars  E  E1  =  a  0,  F  F1  =  b  f\  and  G  G1  =  dg.  Draw  curve 
through  the  points  B,  E1,  F:,  G1  and  D.  Repeat  process  for  the 
opposite  side  A  D1,  then  you  have  form  of  full  beam. 

Fourth  Method. — In  Fig.  28,  let  A  B=half  beam,  A  C=camber. 
Describe  A  C  K  with  radius  A  C.  Divide  A  K  and  C  K  into  equal 
parts  and  A  B  into  the  same  number  of  equal  parts  as  A  K,  and  erect 
perpendiculars.  Produce  d  to  meet  E  D,  e  to  meet  G  F,  /  to  meet 
J  H.  Pass  a  curve  through  the  cutting  points,  repeat  for  the  other 
side  A  B1,  and  you  have  an  approximate  method,  which  is  occasionally 
used. 

To  Draw  in  the  Deck  at  Side  Line. — Run  in  the  Sheer  the 
deck  at  the  centre,  and  lift  from  the  Half  Breadth  the  half  ordinates 
of  the  deck  at  about  every  fifth  frame.  Set  these  points  a,  b,  c,  d,  e, 
and  /  out  square  on  each  side  of  the  centre  A  B  in  Fig.  29 — the 
camber  curve.  Stretch  a  line  across  from  point  to  point,  a  to  a1,  b  to 
b\  and  so  on,  and  measure  the  amount  of  camber  due  to  the  width, 
B  a'2  for  section  a  a1,  B  b2  for  b  b},  etc.,  and  place  these  distances 
below  the  deck  at  the  centre,  which  are  points  for  the  curve  of  side. 
Forward  the  line  should  terminate  on  the  inside  of  the  stem,  aft 
usually  on  the  centre.  At  the  extreme  ends,  owing  to  the  rapid 
reduction  of  widths,  this  line  will  take  a  sudden  rise  to  the  centre  line. 

Expansion  of  the  Deck  Surface. — Girth  in  the  Sheer  the 
deck  line  at  centre  for  the  position  of  the  frame  stations,  stem  and 
stern  points.  Lay  the  batten  on  a  straight  line  and  mark  frame 
stations,  etc.,  from  which  erect  perpendiculars.  Set  out  square  to 
the  centre  on  the  camber  curve  the  half  beam  at  each  section,  and 
girth  the  distances  of  these  points  around  the  curve  relative  to 
the  middle  line.  Place  the  girths  on  their  respective  perpendiculars 
in  the  expansion,  and  draw  curve  through  the  spots.  Repeat  the 
curve  for  the  other  side,  then  the  enclosed  space  is  a  near  approx- 
imation to  the  deck  area,  which  may  be  calculated  by  Simpson's 
Rules  and  the  open  or  uncovered  spaces  deducted. 

To  Show  a  Tapered  Side  Stringer  Plate  on  the  Deck 
Plan, — In  Fig.  30,  draw  in  position  the  frames  1,  2,  3,  4,  and  5,  and 


36 


naval  architectuim:. 


CO 
CO 

L 


extend  tliem  below  the  centre  line.  Make  F1  F2  equal  to  half  the  width 
of  the  stringer  plate  at  the  end.  Draw  F1  F  produced.  On  No.  1,  the 
half  length,  set  off  1  a  the  width  of  the  plate  at  the  half  length,  and 
on  F1  F  the  width  at  the  other  end,  F1  h.  Join 
a  to  h.  Line  in  centre  E  F  and  transfer  it  on  to 
the  plan  above,  E1  F1,  by  making  l1  E1,  21  22, 
31  32,  etc.,  equal  to  1  E,  2  r2,  3  d2,  etc.,  respectively, 
and  square  to  the  line  E1  F1.  Set  off  on  l1  a1,  21  c\ 
31  d\  etc.,  the  widths  of  the  plate,  1  a,  2  c,  3  d,  etc., 
and  pass  curve  through  the  points,  which  gives  the 
inner  edge  of  the  stringer  plate.  This  is  the  method 
usually  adopted.  A  more  correct  one  is  to  girth 
the  line  E1  F1  for  the  position  of  the  frames  and 
lay  them  off  as  shown  on  the  centre  line  and  mark 
off  on  the  expanded  length  the  width  at  the  end. 
Join  the  point  with  a,  shown  by  a  dotted  line. 
Measure  the  widths  at  each  expanded  frame  station 
and  mark  them  off  on  E1,  22,  32,  42,  and  so  on. 
This  gives  a  slightly  fuller  line.  It  is,  perhaps,  in 
practical  work  of  no  great  importance. 

Iron  or  Steel  Deck  Plate  Edges. — They 
are  made  parallel  to  the  centre  line  in  the  expan- 
sion plan  Fig.  31.  The  side  stringer  plate  inside 
edge  is  parallel  to  the  deck  at  side  for  the  half 
length  amidships,  and  tapered  at  the  ends  in  the 
manner  already  described.  Where  no  wood  deck 
is  laid  the  strakes  are  made  in  and  out,  but  when 
a  wood  deck  has  to  be  laid  (see  Fig.  32)  the  strakes 
are  sunken  and  raised,  and  the  inside  edges  of  the 
stringer  plate  may  be  straight  between  the  butts. 
Wide  Stringer  Plates. — In  the  case  of  very 
wide  plates,  the  inner  edge  may  be  arranged  parallel  to  the  centre 
line  for  half  length,  and  worked  in  two  strakes,  shown  in  Fig.  33,  then 
gradually  tapered  towards  the  ends.  This  is  the  method  adopted  in 
war  vessels,  and  there  seems  no  reason  why  it  should  not  be  generally 
carried  out  in  merchant  work. 


Fig.  30. 


T"T 


I    I 


■+- 


Fig.    32. 


grtiBR^ 


or  TBS 


Of  CALlfOj^ 


34. 
FLOORS 


Fig.  34. 
CURVED     FLOORS. 


LEVEL      LINE 


~T7, 


LEVEL      \    LINE 


17 


\f   t   B 


AFTER    BODY. 


EXPANSION 


FORE    BODY. 


PLAN 


FLOORS  AND   DOUBLE   BOTTOMS  37 


CHAPTER  IV. 

Turned-up  Floors:  To  obtain  the  Form— Diminishing  Line  Fairing-up — 
Extreme  End  Floors — Expansion.  Cellular  Double  Bottoms :  How  to 
Obtain  and  Fair  the  Double  Bottom— Expansion  of  the  Inner  Bottom — 
Expansion  of  the  Margin  Plate  — Obtaining  Tank  Knees — Abaft  and  For- 
ward of  Double  Bottom — Expansion  of  Double  Bottom  Floors — Mclntyre 
Tank — Swan  Conical  Tanks. 


FLOORS  AND  DOUBLE  BOTTOMS. 

Turned-up  Floors. — Occasionally  ships  are  built  without  double 
bottoms  ;  then  the  inner  edge  of  the  floors  are  curved  up  the  bilges. 

To  Obtain  the  Form  of  the  Curved  Floors, — Draw  down  in 
the  Body,  on  \  inch  or  f  inch  scale,  the  form  of  about  every  sixth 
frame,  extending  from  the  base  line  to,  say,  6  feet  up.     (See  Fig.  34.) 

The  depth  of  the  floor  at  the  centre  line  is  constant,  and  is  settled 
by  the  Classification  Society's  rules.  By  these  rules  the  midship  floor 
must  not  be  less  than  half  the  centre  depth,  at  a  distance  of  three- 
fourths  of  the  half  breadth  of  the  vessel  set  out  from  the  middle  line 
on  the  run  of  the  frame,  and  not  less  at  the  extreme  ends  than  the 
moulding  of  the  frames ;  and  they  are  required  to  extend  in  a  fair 
curve  well  up  the  bilges,  and  in  no  case  to  terminate  lower  at  the  out- 
side of  the  frame  than  a  perpendicular  height  of  twice  the  midship 
depth  of  the  floor  above  the  top  of  the  keel.  The  figure  shows  the 
Body  sections  in  which  the  height  A  B  is  maintained  on  all  floors  for 
one-fourth  of  the  vessel's  length  amidships,  then  they  are  gradually 
reduced  forward  and  aft  until  the  upper  edge  of  the  floors  are  level 
with  the  midships,  when  they  are  put  in  straight.  G  F  is  level  on  all 
for  the  centre  keelson  bars.  In  ships  with  exceptionally  great  rise  of 
bottom  the  depth  at  the  side  should  be  increased  ;  and  those  with 
very  flat  bottoms,  the  depth  at  f  out  should  be  increased.  The 
reason  for  this  will  be  evident  in  laying  the  curve  off. 

In  the  first  case,  draw  in  the  top  edge  of  the  midship  floor  in  both 
bodies,  according  to  the  above  rule,  and  make  a  skeleton  wood  mould 
from  the  centre  outover,  marking  on  it  the  point  E:  BE  being  equal 
to  the  moulded  frame.  Let  A  B  and  A1  B1,  on  both  sides,  be  the 
height  for  one-fourth  length  amidships.  From  the  point  A  draw  in 
what  is  called  the  "diminishing  line,'"  cutting  the  centre  line  at  C, 


OF  THS 


UNIVERSITY 
^califor^ 


FLOORS   AND   DOUBLE   BOTTOMS  37 


CHAPTER  IV. 

Ti.irned-np  Floors:  To  obtain  the  Form— Diminishing  Line  -Fairing-up — 
Extreme  End  Floors — Expansion.  Cellular  Double  Bottoms:  How  to 
Obtain  and  Fair  the  Double  Bottom— Expansion  of  the  Inner  Bottom — 
Expansion  of  the  Margin  Plate  — Obtaining  Tank  Knees — Abaft  and  For- 
ward of  Double  Bottom — Expansion  of  Double  Bottom  Floors — Mclntyre 
Tank — Swan  Conical  Tanks. 


FLOORS  AND  DOUBLE  BOTTOMS. 

Turned-up  Floors.  —  Occasionally  ships  are  built  without  double 
bottoms  ;  then  the  inner  edge  of  the  floors  are  curved  up  the  bilges. 

To  Obtain  the  Form  of  the  Curved  Floors. — Draw  down  in 
the  Body,  on  \  inch  or  f  inch  scale,  the  form  of  about  every  sixth 
frame,  extending  from  the  base  line  to,  say,  6  feet  up.     (See  Fig.  34.) 

The  depth  of  the  floor  at  the  centre  line  is  constant,  and  is  settled 
by  the  Classification  Society's  rules.  By  these  rules  the  midship  floor 
must  not  be  less  than  half  the  centre  depth,  at  a  distance  of  three- 
fourths  of  the  half  breadth  of  the  vessel  set  out  from  the  middle  line 
on  the  run  of  the  frame,  and  not  less  at  the  extreme  ends  than  the 
moulding  of  the  frames :  and  they  are  required  to  extend  in  a  fair 
curve  well  up  the  bilges,  and  in  no  case  to  terminate  lower  at  the  out- 
side of  the  frame  than  a  perpendicular  height  of  twice  the  midship 
depth  of  the  floor  above  the  top  of  the  keel.  The  figure  shows  the 
Body  sections  in  which  the  height  A  B  is  maintained  on  all  floors  for 
one-fourth  of  the  vessel's  length  amidships,  then  they  are  gradually 
reduced  forward  and  aft  until  the  upper  edge  of  the  floors  are  level 
with  the  midships,  when  they  are  put  in  straight.  G  F  is  level  on  all 
for  the  centre  keelson  bars.  In  ships  with  exceptionally  great  rise  of 
bottom  the  depth  at  the  side  should  be  increased  ;  and  those  with 
very  flat  bottoms,  the  depth  at  f  out  should  be  increased.  The 
reason  for  this  will  be  evident  in  laying  the  curve  off. 

In  the  first  case,  draw  in  the  top  edge  of  the  midship  floor  in  both 
bodies,  according  to  the  above  rule,  and  make  a  skeleton  wood  mould 
from  the  centre  outover,  marking  on  it  the  point  E:  BE  being  equal 
to  the  moulded  frame.  Let  A  B  and  A1  B1,  on  both  sides,  be  the 
height  for  one-fourth  length  amidships.  From  the  point  A  draw  in 
what  is  called  the  "diminishing  line,"  cutting  the  centre  line  at  C, 


38  NAVAL  ARCHITECTURE. 

which  is  about  one-third  of  the  centre  depth  below  the  top  of  the  floor. 
Occasionally  this  line  is  curved.  The  point  c  depends  upon  the  fine- 
ness of  the  ship's  bottom.  Set  off  square  at  each  section,  where  the 
diminishing  line  cuts  the  frame,  the  moulded  width  of  the  frame  B  E. 
Place  the  point  E,  on  the  mould,  fair  with  each  of  the  points  E,  a, 
l>,  r,  etc.,  in  succession,  and  the  edge  of  the  mould  with  F,  and  chalk 
in  to  the  mould  curve  every  section  floor.  Repeat  the  process  in  the 
fore  Body  ;  then  you  have  approximately  the  form  of  the  floors. 

Fairing=up  the  Curved  Floors. — The  inner  edge  only  requires 
fairing,  so  that  the  surface  may  be  fair  for  keelsons  and  ceiling  ; 
and  this  is  best  done  by  diagonals  like  J  II  and  L  K,  made  square 
to  the  curves,  the  distances  of  the  floor  edges  being  lifted  from  .1  and 
L  and  faired,  by  the  contracted  method,  in  the  Sheer  plan.  The 
general  custom  is  to  use  buttocks,  lifting  the  cutting  points  of  the 
curves  on  each  buttock  above  the  base  line  and  fairing  on  contracted 
frame  spacing. 

The  extreme  End  Floors  are  level  on  the  top  edge  and  made 
deeper,  like  Figs.  35  and  36,  to  form  an  efficient  connection  between 
the  sides  of  the  ship,  and  sufficiently  wide  between  the  inside  of 
the  frames  at  the  different  heights  //,  b,  /',  etc.,  in  Fig.  35,  to  lit  the 
keelson  bars  in.  This  point  should  be  found  for  a  few  floors,  and  lines 
ah  and  a1/1  put  through  the  spots  and  faired-up.  Those  stepping 
up  the  stem  and  stern  post  are  made  deeper  to  give  a  good  connec- 
tion. The  transom  floor  must  be  one  and  a  half  times  the  depth  of 
the  midship  floor,  or  the  strength  made  up  in  some  other  way.  In  the 
case  of  a  screw-steamer,  the  depth  of  the  forward  floors  is  decided  in 
the  same  manner  as  in  Fig.  35 ;  the  after  ones  must  be  arranged  suit- 
ably to  stiffen  the  stern  and  to  clear  the  stern  tube — Fig.  36  shows 
the  general  character  of  the  same  with  straight  tops. 

Expansion  of  the  Curved  Floors.— Draw  down,  underneath 
the  Body  sections,  two  parallel  lines,  N  N1  and  P  P1,  distance  apart 
the  depth  of  the  midship  floor  at  the  centre  ;  then  girth  each  floor  for  its 
true  half  length  along  the  middle  of  its  depth,  shown  by  a  dotted 
line  w  ■>■  on  the  midship  floor  ;  and  set  these  lengths  along  M  X  from 
M,  and  drop  perpendiculars  from  the  points,  like  N  n,  equal  to  the 
width  of  the  frame,  which  is  the  width  of  the  floors  at  the  ends,  and 
seeing  that  the  ends  are  all  the  same  width,  an1  may  be  drawn  in 
parallel  to  M  N1.  Set  off  on  w  x  distances  about  one  foot  apart, 
beginning  at  the  centre  line  :  also  on  M  N  set  the  same,  and  drop 
perpendiculars  from  the  points.     Then  lift  the  width  of  each  floor  on 


(0 

CO 


(0 

CO 

tab 


FLOORS  AND  DOUBLE  BOTTOMS.  41 

these  points  square  to  the  dotted  line  w  x  placed  in  each  section,  and 
lay  them  off  in  the  expansion  plan  from  the  top  M  N  on  their  corre- 
sponding distances  from  the  centre.  Make  R  0  the  width  of  the  keel 
bar  and  parallel  to  the  top.  Then  a  curve  passed  through  each  set  of 
spots  will  give  the  true  form  of  the  plate  required.  Repeat  the 
process  in  the  fore  body.  In  ordering  the  plates,  the  bottom  edge  is 
enclosed  by  straight  lines,  which  will  give  one  or  more  knuckles  on 
the  plate,  shown  in  the  after  expansion  by  points  S,  T,  V,  X,  and  R. 
The  intermediate  floors  are  got  by  dividing  the  space  in  between  the 
section  points,  or  by  running  lines  for  the  top  and  knuckle  edges  in 
the  Half  Breadth.  It  is  necessary,  in  ordering  from  the  manufac- 
turer, to  give  the  extreme  length  on  the  top  edge  like  M  N,  also  the 
distances  from  the  centre  to  the  various  knuckles  with  the  squared 
depth  thereat.  In  other  words  to  give  sketches  of  each  class  of  floor 
with  tabulated  sizes.  Some  of  the  shipbuilders  give  the  actual  widths 
of  the  floors  at  about  every  foot,  and  allow  the  mills  to  cut  the  lower 
edge  to  embrace  all  these  widths  ;  and  this  seems  to  be  the  easiest 
way  for  both  shipbuilders  and  millmen,  if  the  widths  are  taken  close 
and  at  uniform  distances  from  the  centre  on  every  floor,  accompanied 
with  one  sketch  showing  the  ends,  centre,  and  distances  apart  of 
the  ordinates.  When  the  floors  extend  the  fall  width  of  the  ship  in 
one  piece,  the  total  lengths  must  be  given  with  the  sketch.  If  the 
floors  are  cut  at  the  centre,  two  plates  will  be  required  for  each  frame. 
Sometimes  they  are  butted  at  different  sides  on  alternate  frames  about 
3  feet  away  from  the  centre  line,  which  requires  two  sketches  for  each 
set  of  floors  and  dimensions  to  suit.  Allowance  to  be  made  for 
butting  if  overlapped. 

Cellular  Double  Bottoms. — Most  of  the  screw  steamers  now 
built  are  fitted  with  double  bottoms  to  carry  water  ballast,  and  in  some 
cases  large  sailing  ships  are  also  fitted  in  this  manner.  The  depth  of 
the  double  bottom  or  tank  at  the  centre  line  should  be  such  that  the 
bottom  is  easily  accessible  by  man-holes  through  the  floors  at  all 
points,  and  yet  allow  in  way  of  the  man-holes  sufficient  effective 
material  to  sustain  probable  ordinary  strains.  Care  should  be 
exercised  that  the  man-hole  cut  out  is  in  the  centre  of  the  depth  of 
the  floor.  If  the  vessel  is  built  under  classification  supervision  the 
centre  depth  ranges  from  about  32  to  48  inches. 

How  to  Obtain  the  Lines  and  Fair  the  Double  Bottom. — 
When  the  centre  depth  A  B  in  Fig.  37  is  settled,  a  line  A  C  is  run 
parallel  to  the  base  line  fib,  showing  the  inner  bottom,  which  is  now 


42'  naval  architecture. 

made  level.  Then  the  width  of  the  flange  or  margin  plate  C  D  is 
decided  upon.  This  should  not  be  less  than  18  inches  to  get  a  suitable 
connection,  and  need  not  exceed  34  inches.  The  width  C  D  is  set  off 
square  to  the  midship  frame  surface  at  such  a  point  that  it  touches 
the  inner  bottom  line  C  A,  and  repeated,  F  G,  H  J,  etc.,  for  about 
every  sixth  frame  in  both  bodies  as  far  as  the  tank  extends.  The 
midship  width  is  maintained,  where  possible,  fore  and  aft ;  but  owing 
to  the  ends  being  much  finer  it  usually  has  to  be  gradually  reduced 
from  about  the  three-quarter  length.  In  some  cases  to  get  a  sub- 
stantial fastening  at  fine  ends  the  top  is  cranked  up.  After  securing 
these  trial  lines  it  is  faired  by  lifting  distances  of  D,  F,  H,  K,  etc., 
square  from  the  centre,  and  placing  them  in  the  Half  Breadth  on 
their  respective  frames  ;  any  correction  for  fairness  made  in  the  Body. 
Then  the  points  C,  G,  J,  L,  etc.,  are  lifted  from  A  and  also  placed  in 
the  Half  Breadth  and  faired.  The  intermediate  spots  are  lifted  from 
these  lines  for  the  scrieve  board.  The  fore  body  sections  are  treated  in 
the  same  manner  for  the  extent  of  the  inner  bottom.  Of  course  the 
after  and  forward  body  lines  should  be  continuous  curves.  Some 
shipbuilders  allow  A  C  to  drop  slightly  towards  the  point  C,  if  the 
taper  on  the  tank  floors  can  be  brought  within  (.)  inches. 

Having  now  obtained  the  lines  and  faired  them,  you  proceed  to 
make  expansions  of  the  various  parts  for  ordering  the  plating. 

Expansion  of  the  Inner  Bottom  Plating. — A  base  line  is 
drawn  representing  the  length  of  the  top  on  a  \  inch  scale.  Per- 
pendiculars are  erected  at  the  frame  stations.  The  widths  on  the  top 
from  the  centre  A  to  the  knuckle  line  C,  G,  etc.,  at  each  frame  are 
lifted  and  set  off'  in  this  expansion  on  their  corresponding  stations, 
and  a  curve  passed  through  the  spots.  Then  the  breadths  of  the 
margin  plate  from  the  knuckle  to  the  frame,  0  D,  G  F,  etc.,  are  lifted 
and  laid  out  from  the  knuckle  line  and  the  curve  drawn.  A  line  not 
less  than  4|  inches  parallel  is  made,  inside  of  this  knuckle,  representing 
the  inner  edge  of  the  margin  plate,  a  in  Fig.  38,  when  hanged  to  take  the 
double  bottom  plating,  which  is  attached  to  it  with  a  single  riveted 
lap.  Next  set  off  parallel  to  the  centre  line  the  position  of  the  inter- 
costal girders  between  the  floors,  and  arrange  top  plating  edges  parallel 
to  the  centre  clear  of  these.  All  the  frames  should  now  be  drawn  across 
the  plan.  Show  the  engine  seating  plating,  position  of  the  1  (linkers, 
boiler  bearers,  engine  girders,  man-holes,  bulkheads,  tunnel,  shell 
plating  butts,  and  whatever  has  to  come  in  contact  with  the  inner 
bottom  plating  ;  after  which  the  butts  may  be  arranged  and  the  plates 


?M    FLOORS 

RWARD 


Fig.   37. 
CELLULAR    DOUBLE    BOTTOM. 


AFTER     BODY 


EXPANSION    OF    INNER    BOTTOM 


FLOORS  AND  DOUBLE  BOTTOMS.  43 

ordered.  It  is  not  a  wise  plan  to  measure  the  lengths  from  the 
drawing  with  a  scale.  A  much  safer  way  is  to  calculate  the  length  of 
tank  top,  and  add  the  amount  required  for  butts,  and  then  work  in 
plates  as  near  as  possible  of  the  same  length — an  allowance  of  £  to 
^  an  inch  on  each  plate  is  sufficient.  The  margin  plate  is  made 
straight  on  its  inner  edge  from  butt  to  butt.  It  will  be  evident 
that  where  the  margin  plate  is  flanged  at  the  knuckle,  a  little  less  in 
the  width  of  plate  would  do,  about  ^  an  inch,  owing  to  the  knuckle 
being  part  of  a  circle,  this  deduction  can  be  easily  made  when  order- 
ing. It  will  also  be  readily  seen  that  this  method  of  expanding  the 
margin  plate,  although  generally  used,  is  on  the  big  side,  which  has 
led  some  shipbuilders  in  these  days  of  economy  to  get  it  more 
accurately  in  the  following  manner:  — 

Expansion  of  the  Margin  Plate. — Place  the  level  line  g  o  in 
the  Body,  Fig.  37.  Lift  points  //,  h,  c,  J,  m,  etc.,  from  the  centre  line, 
and  place  them  in  the  Half  Breadth  on  their  respective  frames.     Then 

girth  this  line  for  the  _.       ^^ 

0  Fig.  38. 

position  of  the  frames 

and  place  these,  ex- 
panded, on  a  straight 
line  about  the  midship 
frame,  from  which 
points  square  lines  in- 
definitely above  and 
below.  Lift  the  widths 
of  the  margin  plate 
below  the  level  line  on 
the  Body  sections  g  D, 
A  F,  etc.,  and  transfer 
them  to  their  respec- 
tive expanded  frame  stations  below  the  level  line.  Pass  a  curve 
through  the  spots  which  will  give  the  lower  edge  of  the  margin  plate ; 
allowance  may  be  made  for  the  point  b,  in  Fig.  38,  being  about  |  inch 
off  the  shell.  The  top  edge  may  be  found  on  a  large  section,  or  on  the 
loft  floor  Body,  by  drawing  the  curve  of  the  plate  and  its  position  on 
the  inner  edge  (see  Fig.  38).  Then  girth  from  //,  //,  i,  etc.,  to  each 
inner  point  a  and  set  these  girths  off  above  the  expansion  line  g  0  on 
their  respective  stations,  and  draw  a  curve  through  the  spots.  This 
is  the  expanded  top  edge  of  the  margin  plate.  The  process  is  repeated 
for  the  fore  body.  The  form  of  this  margin  plate  may  also  be  found 
in  the  same  way  as  the  longitudinal  explained  on  page  132. 


FLOORS  AND  DOUBLE  BOTTOMS.  43 

ordered.  It  is  not  a  wise  plan  to  measure  the  lengths  from  the 
drawing  with  a  scale.  A  much  safer  way  is  to  calculate  the  length  of 
tank  top,  and  add  the  amount  required  for  butts,  and  then  work  in 
plates  as  near  as  possible  of  the  same  length — an  allowance  of  \  to 
^  an  inch  on  each  plate  is  sufficient.  The  margin  plate  is  made 
straight  on  its  inner  edge  from  butt  to  butt.  It  will  be  evident 
that  where  the  margin  plate  is  flanged  at  the  knuckle,  a  little  less  in 
the  width  of  plate  would  do,  about  i  an  inch,  owing  to  the  knuckle 
being  part  of  a  circle,  this  deduction  can  be  easily  made  when  order- 
ing. It  will  also  be  readily  seen  that  this  method  of  expanding  the 
margin  plate,  although  generally  used,  is  on  the  big  side,  which  has 
led  some  shipbuilders  in  these  days  of  economy  to  get  it  more 
accurately  in  the  following  manner  :  — 

Expansion  of  the  Margin  Plate. — Place  the  level  line  g  o  in 
the  Body,  Fig.  37.  Lift  points  //,  h,  c,  /,  m,  etc.,  from  the  centre  line, 
and  place  them  in  the  Half  Breadth  on  their  respective  frames.     Then 

girth  this  line  for  the  _,.       ^_ 

&  Fig.  38. 

position  of  the  frames 

and  place  these,  ex- 
panded, on  a  straight 
line  about  the  midship 
frame,  from  which 
points  square  lines  in- 
definitely above  and 
below.  Lift  the  widths 
of  the  margin  plate 
below  the  level  line  on 
the  Body  sections  g  D, 
It  F,  etc.,  and  transfer 
them  to  their  respec- 
tive expanded  frame  stations  below  the  level  line.  Pass  a  curve 
through  the  spots  which  will  give  the  lower  edge  of  the  margin  plate ; 
allowance  may  be  made  for  the  point  b,  in  Fig.  38,  being  about  ^  inch 
off  the  shell.  The  top  edge  may  be  found  on  a  large  section,  or  on  the 
loft  floor  Body,  by  drawing  the  curve  of  the  plate  and  its  position  on 
the  inner  edge  (see  Fig.  38).  Then  girth  from  <j,  //,  i,  etc.,  to  each 
inner  point  a  and  set  these  girths  off  above  the  expansion  line  g  0  on 
their  respective  stations,  and  draw  a  curve  through  the  spots.  This 
is  the  expanded  top  edge  of  the  margin  plate.  The  process  is  repeated 
for  the  fore  body.  The  form  of  this  margin  plate  may  also  be  found 
in  the  same  way  as  the  longitudinal  explained  on  page  132. 


44  NAVAL  ARCHITECTURE. 

Obtaining  Tank  Knees. — The  tank  knees  are  next  drawn  in. 
The  point  E  X  on  the  midship  frame  is  fixed  as  per  the  Classification 
Society's  rules,  and  a  diminishing  line  X  Y  is  drawn  in  each  Body  for 
the  height  of  all  knees  on  the  frame  edge.  This  line  should  be  at 
the  after  and  forward  extremities  sufficiently  high  to  get  a  good 
connection  for  the  knee.  Then  the  points  C,  (i,  J,  etc.,  are  joined  to 
the  "diminishing  line"  at  their  respective  frames.  Occasionally  the 
knees  are  hollow  between  these  extreme  points,  and  sometimes  the 
knee  is  kept  about  f  inch  below  the  points  C,  (I,  etc. 

Abaft  and  Forward  of  the  Double  Bottom. — In  Figs.  39 
and  36  the  extent  of  the  inner  bottom  is  shown,  and  the  height  of 
the  floors  indicated  before  and  abaft  of  it.  These  are  ordered  in  the 
usual  way,  being  all  straight  on  the  top  edge. 

Expansion  of  the  Double  Bottom  Floors. — Draw  down 
under  Fig.  37,  level  line  C1  C2  for  the  top  of  the  floors,  on  to  which 
square  down  points  C,  G,  J,  etc.,  and  trace  form  of  each  section  in  as 
shown,  which  may  be  easily  done  on  close  buttock  lines  shown  dotted 
in  the  expansion.  In  ordering  enclose  the  curved  bottom  edge  by 
straight  lines,  giving  a  series  of  knuckles.  Some  give  the  depth  from 
the  top  edge  to  the  curve  on  close  spaced  buttocks,  and  allow  the 
mills  to  sheer  the  plate  edge,  between  the  buttocks,  which  is  very  small. 
The  depth  at  and  outstretch  from  the  centre  must  be  given  at  I)  W. 
The  intermediate  floors  are  found  by  "  running  "  the  top  and  knuckle 
points  in  the  Half  Breadth.  Those  on  the  buttocks  may  be  found 
by  "  inspection." 


Note. — In  a  few  cases  the  old  Mclntyre  tank  is  still  fitted.  The  tank  side 
and  top  are  the  same  as  the  cellular  bottom,  only  the  floors  are  shallow  and 
straight.  Continuous  fore  and  aft  girders  being  fitted  between  the  floors  and 
the  inner  bottom.  The  only  difference,  as  far  as  laying  off'  is  concerned,  is  that 
the  floors  are  straight  and  level  on  the  top  edge.  The  Swan  conical  tank  has 
been  fitted  in  some  cases  ;  but,  seeing  the  purpose  for  which  it  was  invented 
has  passed  out  of  use,  it  is  not  described  here. 


I    \J  I    \    V   V  '    111 


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LOAD  DRAFT 


LIGHT    DRAFT 


SHELL  PLATING.  45 


CHAPTER  V. 

Shell  Plating  :  Obtaining  the  Sight  Edges— Lining  Off  the  Model-  Fairing  the 
Sight  Edges  on  the  Model,  on  the  f  lines,  on  the  Loft  Floor — Transfer- 
ing  the  Sight  Edges  to  the  Scrieve  Board— Ordinary  Shell  Expansions- 
Area  of  the  Outer  Bottom  Ordering  the  Shell  Plating  -  Stern  Expansion, 
obtaining  Time  Form  of  Plating,  Check  on  the  Expansion  —Another 
Method  of  Stern  Expansion  — Tumblediome  Stern  Expansion. 


SHELL  PLATING. 

Obtaining  the  Sight  Edges. — Those  are  called  sight  edges 
which  are  visible  on  the  outside,  and  they  are  first  obtained  on  the 
office  Sheer  Draught  in  the  following  manner  : — Mark  off  on  the  Body 
plan  midship  section  in  Fig.  40,  on  each  side,  the  sight  edges  of  the 
sheer  and  garboard  strakes.  It  is  usual  to  place  the  top  edge  of  the 
sheer  strakes  from  10  to  12  inches  above  the  upper  deck  moulded 
line.  The  garboards  are  flanged  down  unto  the  bar  keel  to  within  half 
an  inch  of  the  bottom  of  the  keel.  These  two  points  fixed,  divide  the 
sight  edges  of  the  intermediate  strakes  in  equal  or  suitable  widths,  or 
lift  the  widths  from  the  \  inch  "  Scantling  Section,"  on  which  they  are 
commonly  arranged  to  suit  the  Classification  Society's  rules.  Amidships, 
for  about  the  half  length,  above  the  light  draft  line,  the  edges  are 
sheered  to  the  upper  deck,  W  Y  being  midship  width,  and  from  this 
point  in  the  after  body  they  are  run  square  to  the  frame  curve  to 
reduce  the  amount  of  curvature  or  "  sny  "  on  the  plates.  In  the  fore 
body  from  about  the  half  length  to  the  stem  they  may  be  reduced  in 
width  from  1  to  3  inches,  and  drawn  in  a  fair  curve.  Those  below  the 
light  line,  in  both  bodies,  should  be  sketched  in  about  parallel  girths  for 
the  half  length,  and  then  run  in  straight  to  the  stem  and  stern  posts 
about  square  to  the  frame  curve.  Many  shipbuilders  make  all  the  lower 
edges  straight  in  the  Body.  It  is  best,  if  you  can,  to  arrange  the 
strake  taking  the  screw  boss  in  one  plate  and  an  outside  strake. 
This  cannot  always  be  done,  because  of  the  plate  being  too  large  for  the 
furnace,  and  other  points  of  consideration  of  more  importance  to  the 
shipbuilder.  Owing  to  the  girth  of  the  frames  decreasing  considerably 
towards  the  ends,  it  is  requisite  to  stop  one  or  more  of  the  edges  some 
distance  from  the  stem  and  stern.  A  strake  of  this  description  is 
called  a  "  lost  strake  "  or  stealer.  Fig.  40  shows  the  plate  edges  of  a 
screw  steamer  somewhat  disposed  on  this  plan. 


*fp    LIBRAE 
&'    or  tbs 

UNIVERSITY 

OF  CAUfO*^* 


SHELL  PLATING.  45 


CHAPTER  V. 

Shell  Plating  :  Obtaining  the  Sight  Edges —Lining  Off  the  Model— Fairing  the 
Sight  Edges  on  the  Model,  on  the  §  lines,  on  the  Loft  Floor — Transfer  - 
ing  the  Sight  Edges  to  the  Scrieve  Board  — Ordinary  Shell  Expansion—- 
Area  of  the  Outer  Bottom  Ordering  the  Shell  Plating  -  Stern  Expansion, 
obtaining  True  Form  of  Plating,  Check  on  the  Expansion— Another 
Method  of  Stern  Expansion —Tumble-home  Stern  Expansion. 


SHELL  PLATING. 

Obtaining  the  Sight  Edges. — Those  are  called  sight  edges 
which  are  visible  on  the  outside,  and  they  are  first  obtained  on  the 
office  Sheer  Draught  in  the  following  manner  : — Mark  off  on  the  Body 
plan  midship  section  in  Fig.  40,  on  each  side,  the  sight  edges  of  the 
sheer  and  garboard  strakes.  It  is  usual  to  place  the  top  edge  of  the 
sheer  strakes  from  10  to  12  inches  above  the  upper  deck  moulded 
line.  The  garboards  are  Hanged  down  unto  the  bar  keel  to  within  half 
an  inch  of  the  bottom  of  the  keel.  These  two  points  fixed,  divide  the 
sight  edges  of  the  intermediate  strakes  in  equal  or  suitable  widths,  or 
lift  the  widths  from  the  h  inch  "  Scantling  Section,"  on  which  they  are 
commonly  arranged  to  suit  the  Classification  Society's  rules.  Amidships, 
for  about  the  half  length,  above  the  light  draft  line,  the  edges  are 
sheered  to  the  upper  deck,  W  Y  being  midship  width,  and  from  this 
point  in  the  after  body  they  are  run  square  to  the  frame  curve  to 
reduce  the  amount  of  curvature  or  "  sny  "  on  the  plates.  In  the  fore 
body  from  about  the  half  length  to  the  stem  they  may  be  reduced  in 
width  from  1  to  3  inches,  and  drawn  in  a  fair  curve.  Those  below  the 
light  line,  in  both  bodies,  should  be  sketched  in  about  parallel  girths  for 
the  half  length,  and  then  run  in  straight  to  the  stem  and  stern  posts 
about  square  to  the  frame  curve.  Many  shipbuilders  make  all  the  lower 
edges  straight  in  the  Body.  It  is  best,  if  you  can,  to  arrange  the 
strake  taking  the  screw  boss  in  one  plate  and  an  outside  strake. 
This  cannot  always  be  done,  because  of  the  plate  being  too  large  for  the 
furnace,  and  other  points  of  consideration  of  more  importance  to  the 
shipbuilder.  Owing  to  the  girth  of  the  frames  decreasing  considerably 
towards  the  ends,  it  is  requisite  to  stop  one  or  more  of  the  edges  some 
distance  from  the  stem  and  stern.  A  strake  of  this  description  is 
called  a  "  lost  strake  "  or  stealer.  Fig.  40  shows  the  plate  edges  of  a 
screw  steamer  somewhat  disposed  on  this  plan. 


46 


NAVAL  ARCHITECTURE. 


Lining  Off  the  Model.— A  half  block  model  of  the  ship  is  made 
on  a  scale  of  a  quarter  of  an  inch  equal  to  1  foot.  The  back  is  slightly 
beyond  the  centre  line  as  shown  in  Fig-.  41,  for  marking  off  on  the 
keel  the  frame  stations.  The  top  is  flush  to  the  rail  line  or  poop  and 
forecastle  decks,  as  the  case  may  be.  This  model  is  painted  white  and 
smoothed  down,  or  varnished.     The  top  and  back  are  not  painted. 

Fig.  41. 


?l^ 


S1 


^fe* 


K\\\\\\\\\\\\\\\\\\\V0*te 

i^w  PLAN 


BRACKET 


MODEL 


The  upper  deck  line  should  be  set  off  on  the  midship  frame,  and 
then  run  in  fore  and  aft  with  a  gauge  parallel  to  the  top  line.  If  not 
parallel  it  is  lined  in  with  a  batten  attached  with  pins  or  eyeless 
oeedles.  The  model  is  laid  upon  a  thick  drawing  board  C,  and  the 
position  of  the  frames  marked  on  the  bottom  centre  by  producing 
the  model  maker's  section  lines  from  the  back,  and  setting  off  the 
intermediates.  This  producing  is  done  with  a  joiner's  set  square. 
The  stations  are  also  squared  across  the  top  from  the  back  to  act  as 


SHELL  PLATING.  47 

a  guide  in  lining  in  the  frames  ;  which  is  done  with  a  drawing-pen 
and  ink,  or  with  a  pencil,  by  placing  brackets  B  of  various  form 
across  the  model  to  guide  the  pen  or  pencil  holder  H,  made  with  a 
flat  side  to  slide  easily  and  steadily  against  the  face  of  the  bracket. 
The  palm  edge  B1  is  perfectly  square  to  the  face  B,  and  is  worked 
close  up  against  the  keel,  and  so  fixed  to  the  frame  station  that 
the  pen  will  trace  through  the  spot.  "When  all  the  frames  are  drawn 
across  the  model,  the  position  of  the  shell  plate  sight  edges  are 
lifted,  relative  to  the  upper  deck  and  centre  line,  on  narrow  strips  of 
drawing  paper.  This  is  done  by  girthing  the  body  sections  (on  the 
same  scale  as  the  model),  and  marking  centre,  plate  edges,  and  decks, 
and  transferring  the  girthed  spots  to  the  model  on  corresponding 
frames.  Thin  narrow  yellow  pine  battens  of  parallel  width  are  pinned 
to  the  spots,  and  the  lines  faired  and  inked  or  pencilled  in,  and  cor- 
rections, if  any,  made  in  the  Body.  The  battens  may  be  kept  in 
position  by  strong  elastic  bands  passed  round  the  model.  The 
stringers,  keelsons,  and  inner  bottom  side  are  lined  off  in  the  same 
way.  Then  the  butts  of  the  shell  plating,  stringers,  keelsons,  etc.,  are 
transferred  from  the  "  shell  expansion,"  or  arranged  by  the  draftsman 
on  the  model.  It  is  usual  to  line-off  all  wash  ports,  scuppers, 
sidelights,  openings  in  the  shell,  erection  fronts,  bulkheads,  liners, 
doublings,  alphabetical  letter  of  strake,  number  of  plate,  thickness  of 
plate ;  and  to  indicate,  by  various  colours,  treble,  double,  and  single 
riveted  butts.  Many  shipbuilders  show  the  character  of  butts  by 
cross  lines,  one  line  standing  for  single,  two  for  double,  and  three  for 
treble.  The  shell  plating  is  usually  ordered  from  this  model,  so  that 
it  is  necessary  that  the  marking  off  should  be  done  with  care  and 
completeness. 

Fairing  Plate  Edges  on  f  inch  Lines. — In  this  case  the 
plate  edges  are  obtained  on  the  f  inch  scale  Body  sections  in  the 
manner  already  described.  Those  above  the  light  draught  line  are 
faired-up  in  the  Sheer  by  lifting  at  each  sectional  frame  the  perpen- 
dicular distance  like  T  S  from  the  base  to  the  intersection  of  the  plate 
edge  and  frames,  and  setting  the  heights  above  the  base  in  the  Sheer 
on  their  corresponding  frames  Those  below  the  light  line  are  lifted 
square  out,  like  0  P,  from  the  centre  line  to  the  frame  and  plate  edge 
intersection  and  laid-off  in  the  Half  Breadth.  Of  course  the  correct 
terminations  must  be  found  by  projecting  the  cutting  points,  as  in  u, 
on  the  half  siding  into  the  Sheer  on  the  inside  of  the  posts,  and  from 
there  into  the  Half  Breadth.  Any  modification  necessary  for  fairness 
is  made  in  the  Body. 


48  NAVAL  ARCHITECTURE. 

Fairing   Plate   Edges   on   the    Loft   Floor. — Carry  out   the 
same  method  as  explained  for  the  f  inch  lines. 

Transferring  Shell  Sight  Edges  to  the  Scrieve  Board. — 

The  position  of  the  sight  edges  on  a  few  sections  may  be  girthed  and 
given  to  the  loftsman,  but  what  appears  a  better  plan  is  to  draw 
straight  lines  from  the  post  to  the  midship  point,  like  a  I>,  c //,  <■  f\ 
and  g  h,  in  Fig.  40,  and  girth  the  distance  on  the  frames  from  these 
lines  to  the  sight  edge.  If  the  loftsman  is  supplied  with  a  copy  of 
these  sections  with  the  lines  and  distances  on,  and  the  vertical  height 
on  the  midship  section  frame  and  centre  line,  he  ought  to  have  little 
or  no  difficulty  in  transferring.  Of  course,  consideration  should  be 
given  to  any  alteration  found  necessary  in  the  scrieve  midship  widths. 
The  Ordinary  Method  of  making  a  Shell  Expansion. — 
In  Fig.  42,  set  off  to  a  quarter  inch  scale  the  length  of  the  ship  on  a 
base  line  T  F,  and  lift  the  form  of  the  after  end,  ABC,  and  the  fore 
end,  D  E  F,  from  the  Sheer  Draught ;  or  lay  the  model  on  the  base  and 
pencil  round  the  ends.  Mark  off  on  the  base  the  position  of  the  Body 
sections,  and  erect  from  these  points  perpendiculars  of  indefinite 
length.  Then  girth  each  Body  section,  drawn  to  the  same  scale,  from 
the  centre  line  to  the  rail,  for  the  position  of  the  plate  edges,  keelsons, 
decks,  etc.,  and  lay  these  distances  out  on  their  respective  stations 
from  the  base  T  F.  The  terminations  of  these  lines  on  the  inside  of 
the  stem  and  stern  posts  are  lifted  perpendicular  from  the  base  of  the 
Body  on  the  half  siding,  and  transferred  on  to  the  expansion.  The 
shape  of  the  part  abaft  of  the  transom  is  taken  from  the  stern 
expansion.  Lines  may  now  be  run  through  the  spots,  as  shown  in 
Fig.  42,  and  all  the  frames  drawn  in  red  ink  to  their  correct  heights. 
The  transverse  bulkheads,  decks,  keelsons,  tank  side,  and  girders  are 
indicated  by  blue  lines,  and  the  shell  plating  edges,  butts,  openings, 
in  black.  Doubling  plates  should  also  be  shown  in  some  dis- 
tinguishing colour.  This  plan  shows  all  openings  in  the  bottom, 
and  whatever  comes  in  contact  with  it,  besides  the  alphabetical  mark 
of  each  strake,  and  the  number  of  each  plate,  the  size  and  spacing  of 
the  riveting,  the  width  of  the  butt  straps  or  laps,  and  the  seam  edge 
laps,  and  at  least  the  half  and  three-quarter's  length  amidships,  and 
the  change  of  the  frames  or  deadflat.  It  will  be  evident  that  this  is 
not  a  correct  expansion  of  the  shell  plating  ;  and  is,  therefore,  of  no 
use  for  measuring  off  the  size  of  the  plates.  Its  purpose  is  solely  for 
the  guidance  of  the  shell  men  in  plating  the  bottom  of  the  ship, 
which  decides  the  information  to  be  placed  upon  it. 


FIG.    42. 

SHELL      EXPANSION      PLAN 


MP    =    MOORINC    PIPE 
VVP    =    WASH    PORT 
C       =  CANCWAY 
C  D    =    COALINC 


49 


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Fig.  43. 
EXPANSION     OF     FORE     BODY 


IOE  105  108  Hi 


SHELL  PLATING.  49 

Area  of  the  Outer  Bottom  or  Shell  Plating. — An  approxi- 
mate expansion  of  the  shell  plating  may  be  found  by  taking  the  lengths 
of  a  series  of  level  lines,  and  of  a  series  of  transverse  sections,  and 
manipulating  their  intersections  by  two  sets  of  paper  strips.  Pinning 
the  strips  to  the  centre  line  position,  with  freedom  to  move  round  that 
point,  and  connecting  the  cutting  points  of  the  transverse  strips  with 
the  longitudinal  strips,  also  free  to  move,  by  this  means  the  surface  is 
laid  out  approximately  in  a  level  plane.  But  this  is  not  correct  in 
principle,  owing  to  no  account  being  taken  of  the  inclination  of  the 
level  lines  to  the  vertical  sections.  A  more  correct  method  is  by  a 
writer  in  one  of  the  Annuals  of  the  Royal  School  of  Naval  Architec- 
ture, signing  himself  J.  C.  For  instance,  in  Fig.  43  let  a  b  and  d  c 
be  two  sections.  Draw  b  c  and  a  d  as  near  as  possible  square  to  both 
sections  105  and  102.  Then  these  lines,  when  placed  on  the  model, 
will  be  almost  perpendicular  to  each  other.  In  order  to  find  the  area 
of  the  space  enclosed,  it  will  only  be  necessary  to  obtain  the  lengths 
of  b  c  and  a  d,  and  then  construct  the  figures  thus.  In  the  expansion 
make  A  D  =  the  true  length  of  a  d  =  A1  D1.  Erect  perpendicular 
D  C  and  A  B  to  A  D  line,  and  draw  A  B  =  a  b  and  D  C  =  d  c,  and 
join  B  to  0.  This  figure  A,  B,  C,  D,  represents  closely  the  area  of 
the  surface  on  the  model.  Apply  this  principle  to  the  entire  surface. 
Draw  in  the  Body  curved  diagonal  lines,  1,  2,  3,  etc. — shown  faint 
lines — as  near  as  possible  square  to  the  frames  at  their  points  of  inter- 
section. Then  girth  from  the  centre  the  position  of  the  frames  on 
these  lines,  and  set  them  off  in  the  Half  Breadth  as  shown.  Secure 
the  end  terminations  by  squaring  over  into  the  Sheer  the  heights  on 
the  inside  of  the  stem,  and  projecting  down  into  the  Half  Breadth 
on  the  half  siding.  By  this  means  the  true  lengths  on  the  diagonals 
are  got.  Then  apply  these,  beginning  with  the  bottom,  and  set  off 
on  the  stations  in  the  expansion  the  square  breadths  or  girths  of  the 
lowest.  Draw  lines  through  the  spots  thus  obtained,  and  apply  the 
girthed  positions  of  the  frames  taken  from  the  Half  Breadth  on  this 
first  diagonal,  commencing  from  number  66  and  working  therefrom. 
Erect  perpendiculars,  in  the  expansion  to  the  curve  of  first  diagonal 
from  the  points,  and  apply  the  widths  girthed  from  the  Body 
between  one  and  two  diagonals,  and  run  curve  through  the  spots. 
The  position  of  the  frames  for  number  two  diagonal,  taken  from  the 
Half  Breadth,  must  be  set  on  the  line  just  drawn  in,  and  the  girthed 
widths  from  the  Body  set  on  the  perpendiculars  as  before,  which 
will  give  spots  for  another  expanded  diagonal  fine.     The  process  is 

5 


<g£    LIBRAE 


or  tbb 


SHELL  PLATING.  49 

Area  of  the  Outer  Bottom  or  Shell  Plating. — An  approxi- 
mate expansion  of  the  shell  plating  may  be  found  by  taking  the  lengths 
of  a  series  of  level  lines,  and  of  a  series  of  transverse  sections,  and 
manipulating  their  intersections  by  two  sets  of  paper  strips.  Pinning 
the  strips  to  the  centre  line  position,  with  freedom  to  move  round  that 
point,  and  connecting  the  cutting  points  of  the  transverse  strips  with 
the  longitudinal  strips,  also  free  to  move,  by  this  means  the  surface  is 
laid  out  approximately  in  a  level  plane.  But  this  is  not  correct  in 
principle,  owing  to  no  account  being  taken  of  the  inclination  of  the 
level  lines  to  the  vertical  sections.  A  more  correct  method  is  by  a 
writer  in  one  of  the  Annuals  of  the  Royal  School  of  Naval  Architec- 
ture, signing  himself  J.  C.  For  instance,  in  Pig.  43  let  a  b  and  d  c 
be  two  sections.  Draw  b  c  and  a  d  as  near  as  possible  square  to  both 
sections  105  and  102.  Then  these  lines,  when  placed  on  the  model, 
will  be  almost  perpendicular  to  each  other.  In  order  to  find  the  area 
of  the  space  enclosed,  it  will  only  be  necessary  to  obtain  the  lengths 
of  //  c  and  a  d,  and  then  construct  the  figures  thus.  In  the  expansion 
make  A  D  =  the  true  length  of  a  d  =  A1  D1.  Erect  perpendicular 
D  C  and  A  B  to  A  D  line,  and  draw  A  B  =  a  b  and  D  C  =  d  c,  and 
join  B  to  C.  This  figure  A,  B,  C,  D,  represents  closely  the  area  of 
the  surface  on  the  model.  Apply  this  principle  to  the  entire  surface. 
Draw  in  the  Body  curved  diagonal  lines,  1,  2,  3,  etc. — shown  faint 
lines — as  near  as  possible  square  to  the  frames  at  their  points  of  inter- 
section. Then  girth  from  the  centre  the  position  of  the  frames  on 
these  lines,  and  set  them  off  in  the  Half  Breadth  as  shown.  Secure 
the  end  terminations  by  squaring  over  into  the  Sheer  the  heights  on 
the  inside  of  the  stem,  and  projecting  down  into  the  Half  Breadth 
on  the  half  siding.  By  this  means  the  true  lengths  on  the  diagonals 
are  got.  Then  apply  these,  beginning  with  the  bottom,  and  set  off 
on  the  stations  in  the  expansion  the  square  breadths  or  girths  of  the 
lowest.  Draw  lines  through  the  spots  thus  obtained,  and  apply  the 
girthed  positions  of  the  frames  taken  from  the  Half  Breadth  on  this 
first  diagonal,  commencing  from  number  66  and  working  therefrom. 
Erect  perpendiculars,  in  the  expansion  to  the  curve  of  first  diagonal 
from  the  points,  and  apply  the  widths  girthed  from  the  Body 
between  one  and  two  diagonals,  and  run  curve  through  the  spots. 
The  position  of  the  frames  for  number  two  diagonal,  taken  from  the 
Half  Breadth,  must  be  set  on  the  line  just  drawn  in,  and  the  girthed 
widths  from  the  Body  set  on  the  perpendiculars  as  before,  which 
will  give  spots  for  another  expanded  diagonal  line.     The  process  is 

5 


50 


NAVAL  ARCHITECTURE. 


f=~ 


repeated  until  the  surface  is  completed  ;  when  it  may  be  calculated 
by  Simpson's  rules,  the  butts  and  seams  being  got  by  percentage. 
The  frames,  dotted,  appear  curved  lines.  The  position  of  the  decks, 
keelsons,  plate  edges,  may  be  transferred  with  reference  to  the 
diagonals.  In  Fig.  43,  the  decks  and  keelsons  are  dotted  lines  and 
the  plate  edges  thick  lines. 

Ordering  of  the  Shell  Plating. — 
The  nett  widths  at  the  butts  of  each  strake 
are  lifted  from  the  scrieve  board.  This  is 
done  by  marking  on  the  "  boards,"  in  chalk, 
the  position  of  the  butts  between  the 
I  I  frames,  and  girthing  the  line  in  each  case 
for  the  full  width  of  the  strake,  i.e.,  includ- 
ing the  laps.  The  draftsman  makes  an 
allowance  in  ordering  for  the  "sny,"  or 
round  on  the  edge,  which  is  practically  a 
matter  of  judgment.  A  rough  idea  can  be 
got  from  the  model  by  holding  a  scale  along 
the  plate  edge.  One  of  the  best  methods  is 
to  place  a  piece  of  thin  tracing  paper  on 
the  model,  covering  the  plate  lines  from 
butt  to  butt,  and  tracing  carefully  with  a 
pencil  the  top  and  bottom  edges  ABC  and 
FED,  and  the  butts  A  F  and  C  D,  see  Fig. 
44  ;  then  straight  lines  are  drawn  enclosing 
this  trace.  Draw  A  C  and  d  e  to  enclose 
plate,  and  bisect  the  space  by  a  l>,  make 
d  a  f  and  Che  square  to  a  b  ;  then  deCf 
is  the  nett  size  of  the  plate  required  of 
double  taper,  to  which  must  be  added  from 
half  an  inch  to  an  inch  in  the  length  for 
planing.  The  allowances  on  the  breadths 
should  be  very  little  at  midships  in  the  case 
of  the  inside  strakes,  and  from  three-quarters 
to  one  inch  on  the  outside  strakes.  It  is 
usual  to  allow  a  few  inches  in  the  length 
of  the  endmost  plates,  and  also  a  greater  allowance  on  the  widths  of 
the  plates  under  the  counter,  to  meet  any  alteration  made  to  the  plate 
edges  on  the  ship.  A  necessary  precaution,  when  the  ship  is  scrieved 
down,  is  to  girth  a  few  sections  and  test  the  correctness  of  the  model. 


* 

co 

— ! 

a. 

*  1 

.    1 

OX) 

-j 

u.   j 

ui 

I 

W 

SHEER 


\ 


\ 


/ 


v 


STEKN  EXPANSION.  51 

STERN  EXPANSION. 
How  to  Obtain  the  True  Form  of  the  Stern  Plating. — In  Fig. 

45,  produce  A  B  indefinitely  to  C,  and  erect  square  set  lines  B  D  from 
B,  and  A  E  from  A.  Join  A  to  A1  and  B  to  B1.  Through  the  points 
a1,  b1,  c1,  d1,  e1,/1,  and  g1  in  the  Half  Breadth,  draw  level  lines  to  the 
knuckle  perpendicular,  and  drop  perpendiculars  from  a,  b,  c,  d,  e,f,  and 
g  in  the  Sheer  on  to  A  C.  Lift  from  A  C  the  length  of  these  lines  from 
the  knuckle,  and  set  them  forward  of  the  knuckle  perpendicular  BB1, 
on  their  corresponding  level  lines  in  the  Half  Breadth;  for  instance,  J  d 
on  J1  d1.  Pass  a  curve  through  these  spots,  and  you  have  what  is 
called  the  corrected  knuckle  or  "set  line  ;"  girthing  it  from  the  centre 
for  the  points  of  the  cants  and  frames,  e2  will  be  the  mark  for  the 
transom,  and  so  on.  Lay  them  out  in  the  Sheer  from  B  on  B  I),  and 
erect  perpendiculars  of  an  indefinite  length  at  the  points  c/3,  bs,  etc., 
and  then  produce  lines  parallel  to  B  D  through  a,  b,  c,  etc.,  to  meet 
corresponding  perpendiculars :  a  should  cut  a3,  and  so  on.  A  curve 
passed  through  the  intersections  is  the  expanded  knuckle  line.  The 
same  process  is  repeated  for  the  rail,  working  from  A  A1  and  AE  :  by 
which  the  true  moulded  form  of  the  plating  is  got.  Sometimes  an 
additional  set  line  is  put  in  between  the  rail  and  knuckle.  Where  there 
is  much  round  on  the  transom,  it  is  a  wise  plan  to  girth  the  distance 
from  the  knuckle  to  the  rail  in  the  Body,  and  see  that  the  expansion 
is  sufficiently  wide. 

Check  on  the  Stern  Expansion. — Bend  a  lath  round  the  original 
rail  and  knuckle  lines  in  the  Half  Breadth,  and  lift  the  position  of  the 
cants  and  ordinary  frames  relative  to  the  centre  line,  which  try  on  the 
respective  expansion  lines  of  the  rail  and  knuckle  ;  if  correct,  the 
position  of  the  cants,  etc.,  should  agree. 

The  butts  of  the  plating  are  now  arranged  clear  of  the  cants,  etc., 
and  the  plates  ordered,  making  suitable  allowance  at  the  top  and 
bottom  for  connections.  A  wood  template  is  made  of  the  expanded 
edges,  from  the  centre  line  to  the  butt  just  forward  of  the  transom. 
Cross-pieces  are  nailed  on  it,  for  the  moulded  edge  of  the  cants  and 
frames,  over  which  is  marked  the  position  of  the  set  line  B  D.  The 
other  side  of  the  ship  is  simply  duplicated.  The  plater  makes  the 
allowances  for  connection  at  top  and  bottom  over  and  above  the 
template.  A  mould  is  also  given  to  the  yard  showing  the  shape  of 
the  set  line. 

Another  Method  of  Stern  Expansion.  —  In  Fig.  46,  erect  set 
line  A  B  square  to  A  C  from  the  point  A,  and  square  down  on  to  the 
cants  in  the  Half  Breadth  the  intersections  of  this  set  line  with  the  rail 


STEKN  EXPANSION.  51 

STERN  EXPANSION. 
How  to  Obtain  the  True  Form  of  the  Stern  Plating. — In  Fig. 

45,  produce  A  B  indefinitely  to  C,  and  erect  square  set  lines  B  D  from 
B,  and  A  E  from  A.  Join  A  to  A1  and  B  to  B1.  Through  the  points 
a1,  b1,  c1,  d1,  e1,/1,  and  g1  in  the  Half  Breadth,  draw  level  lines  to  the 
knuckle  perpendicular,  and  drop  perpendiculars  from  «,  b,  c,  d,  e,f,  and 
g  in  the  Sheer  on  to  AC.  Lift  from  A  C  the  length  of  these  lines  from 
the  knuckle,  and  set  them  forward  of  the  knuckle  perpendicular  B  B1, 
on  their  corresponding  level  lines  in  the  Half  Breadth:  for  instance,  J  d 
on  J1  d1.  Pass  a  curve  through  these  spots,  and  you  have  what  is 
called  the  corrected  knuckle  or  "set  line ;"  girthing  it  from  the  centre 
for  the  points  of  the  cants  and  frames,  e2  will  be  the  mark  for  the 
transom,  and  so  on.  Lay  them  out  in  the  Sheer  from  B  on  B  D,  and 
erect  perpendiculars  of  an  indefinite  length  at  the  points  as,  bs,  etc., 
and  then  produce  lines  parallel  to  B  D  through  a,  b,  c,  etc.,  to  meet 
corresponding  perpendiculars :  a  should  cut  a3,  and  so  on.  A  curve 
passed  through  the  intersections  is  the  expanded  knuckle  line.  The 
same  process  is  repeated  for  the  rail,  working  from  A  A1  and  AE  :  by 
which  the  true  moulded  form  of  the  plating  is  got.  Sometimes  an 
additional  set  line  is  put  in  between  the  rail  and  knuckle.  Where  there 
is  much  round  on  the  transom,  it  is  a  wise  plan  "to  girth  the  distance 
from  the  knuckle  to  the  rail  in  the  Body,  and  see  that  the  expansion 
is  sufficiently  wide. 

Check  on  the  Stern  Expansion. — Bend  a  lath  round  the  original 
rail  and  knuckle  lines  in  the  Half  Breadth,  and  lift  the  position  of  the 
cants  and  ordinary  frames  relative  to  the  centre  line,  which  try  on  the 
respective  expansion  lines  of  the  rail  and  knuckle  ;  if  correct,  the 
position  of  the  cants,  etc.,  should  agree. 

The  butts  of  the  plating  are  now  arranged  clear  of  the  cants,  etc., 
and  the  plates  ordered,  making  suitable  allowance  at  the  top  and 
bottom  for  connections.  A  wood  template  is  made  of  the  expanded 
edges,  from  the  centre  line  to  the  butt  just  forward  of  the  transom. 
Cross-pieces  are  nailed  on  it,  for  the  moulded  edge  of  the  cants  and 
frames,  over  which  is  marked  the  position  of  the  set  line  B  D.  The 
other  side  of  the  ship  is  simply  duplicated.  The  plater  makes  the 
allowances  for  connection  at  top  and  bottom  over  and  above  the 
template.  A  mould  is  also  given  to  the  yard  showing  the  shape  of 
the  set  line. 

Another  Method  of  Stern  Expansion. — In  Fig.  46,  erect  set 
line  A  B  square  to  A  C  from  the  point  A.  and  square  down  on  to  the 
cants  in  the  Half  Breadth  the  intersections  of  this  set  line  with  the  rail 


52  NAVAL  ARCHITECTURE. 

and  cants,  a,  &,  c,  and  d,  drawing  level  lines  through  these  points 
a\  b\  c1,  and  d1.  Lift  the  distances  d,  c,  1>,  and  a  on  the  run  of  the 
set  line  from  the  point  A,  and  transfer  them  to  their  corresponding 
level  lines  a1,  h,1  e1,  etc.,  in  the  Half  Breadth,  setting  off  to  the  left  of 
the  knuckle  perpendicular.  Next  produce  in  the  Body  the  line  of  the 
T  and  I  frames  indefinitely  above  the  rail,  also  produce  T  and  I 
in  the  Sheer  until  they  cut  the  set  line  A  B,  and  level  over  into 
the  Body  the  cutting  points  c  to  T  and  /  to  I  frame  produced. 
Measure  in  the  Body  the  distance  of  el  and/1  from  the  centre  line,  and 
set  them  off  parallel  lines  to  the  centre  in  the  Half  Breadth  ;  then  lift 
e  and/  on  the  run  of  the  set  line  in  the  Sheer  from  A,  and  lay  them 
out  to  the  left  of  the  knuckle  perpendicular  on  their  corresponding 
level  lines  e2  and  f2.  The  set  line  can  now  be  drawn  through  these 
spots  in  the  Half  Breadth,  which  is  then  girthed  from  the  centre  for 
the  position  of  the  cants,  etc.,  marked  1  r,  2  c,  8  c,  4  c,  5  r,  R,  e2  and/2, 
and  laid-off  on  the  expansion  set  line  from  X.  The  expanded  cants, 
which  are  shown  in  the  Sheer  by  dotted  lines  E  C  5,  E  0  4,  and  E  0  3, 
as  explained  on  page  32,  have  the  points  a,  />,  c,  and  d,  levelled  on  to 
them,  and  are  then  girthed  lengthways  to  the  rail  and  knuckle,  above 
and  below  the  points,  and  with  these  girths  as  radii  describe  arcs  of 
circles  from  the  cant  spots  on  the  corresponding  side  of  the  expansion  set 
line.  For  the  position  of  the  transom  and  I  frames,  in  the  expansion, 
girth  the  distances  in  the  Body  of  e1  and  f1  relative  to  the  rail  and 
knuckle  respectively,  and  with  these  distances  for  radii  describe  arcs 
from  the  points/3  and  e3,  on  the  set  line,  for  the  knuckle  and  rail. 
Next  girth  the  rail  in  the  Half  Breadth  for  the  position  of  the  cants, 
and  bend  the  lath  round  the  arcs  in  the  expansion,  then  the  points  of 
contact  will  be  the  position  of  the  cants,  through  which  draw  curve. 
Do  the  same  with  the  knuckle  line.  The  point  R1  should  agree  with 
the  girthed  distance  on  the  rail  of  /il  from  the  centre  line.  The  cants 
can  now  be  shown  in  the  expansion  through  the  three  points.  The 
position  of  the  buttocks  on  the  expansion  set  line  are  got  by 
girthing  the  Half  Breadth  set  line  fi-om  the  centre  for  their  distances, 
and  setting  them  off  from  X  along  X/3.  The  position  on  the  rail  and 
knuckle  edges  are  found  by  girthing  in  the  Sheer  their  length  to  the 
rail  and  knuckle  respectively  above  and  below  the  set  line,  and 
describing  arcs  of  circles  from  the  points  on  the  expansion  set 
line  as  was  done  for  the  cants.  The  cutting  points  of  these  arcs 
on  the  curve  will  allow  the  buttocks  to  be  drawn  in.  To  prevent 
confusion  they  are  left  out  of  the  Sheer.  If  a  batten  is  bent 
round  either  the  rail  or  knuckle  of  the  Half  Breadth,  and  the  points 


Fig.  46 


w 


STERN     EXPANSION 


Fig.  46. 


BODY 


BODY 


a 

* 

3 


21 
*1 


RAIL 


^    LIBRAE 
OF  CAU?5^* 


BODY 


a 
z 

1 

3 


UNU&ftLE 


RAIL 


LEVF1     1INF 


DC 


Fig.    47. 
IN      EXPANSION 


BODY 


STERN   EXPANSION.  53 

of  the  cants  and  buttocks  lifted  and  girthed  round  the  expanded 
edge  the j  should  agree  with  the  positions  already  indicated  when  the 
plan  is  correct.  The  butts  of  the  plating  are  now  arranged  clear  of 
the  cants  and  the  ordinary  frames,  and  a  skeleton  template  made 
showing  the  expanded  top  and  bottom  edges  with  cross  pieces  nailed 
on  for  the  heel  of  cants,  T,  and  I  frames,  with  the  set  line  marked 
across  them.  The  plater  extends  indefinitely  on  the  boards  the  line 
f3  X  in  the  direction  of  X,  and  turns  the  template  over  to  find  the 
position  of  R1  on  the  line  for  the  reverse  side  of  the  vessel.  Allowance 
in  ordering  and  working  the  plates  should  be  made  on  the  top  and 
bottom  edges  for  connections.  The  plates  are  ordered  to  embrace  the 
curve,  and  care  should  be  exercised  to  see  that  the  plate  is  sufficiently 
wide  to  make  the  connections  at  top  and  bottom. 

Expansion  of  a  Tumble-home  Stern. — The  stern  in  small 
coasters,  tug-boats,  and  river  craft  is  sometimes  formed  as  shown  in 
Fig-  47-  In  that  case  the  expansion  is  somewhat  different  to  that 
already  described.  Show  in  the  Sheer,  Half  Breadth,  and  Body,  the 
initial  faired-up  lines,  i.e.,  the  frames,  buttocks,  rail,  and  knuckle. 
Join  F  to  B  and  G  to  A.  Extent  indefinitely  A  B  to  C.  Erect  per- 
pendiculars or  set  lines  A  D  and  B  E  of  indefinite  length.  Through  points 
a,  b,  c,  d,  e,  /,  and  g  drop  perpendiculars  on  to  B  C,  and  draw  level  lines 
through  the  same  points  in  the  Half  Breadth,  a1,  bl,  c1,  d1,  etc.,  to  the 
rail  vertical.  Lift  in  the  Sheer  the  square  distance  of  the  points  a,  b, 
c,  d,  e,  f,  and  g  from  B  C,  and  lay  them  off  forward  of  F  B  in  the  Half 
Breadth  on  their  respective  level  lines,  and  trace  the  dotted  line 
through  the  spots,  which  is  called  the  corrected  rail  line.  Girth  this 
line  from  the  centre  for  the  new  position  of  the  buttocks  and  frames, 
and  measure  the  distances  out  from  B  on  B  E,  and  from  the  points 
erect  perpendiculars  to  cut  the  lines,  produced,  already  shown 
through  a,  b,  e,  d,  etc.,  which  are  parallel  to  B  E.  The  intersection 
of  corresponding  lines  will  give  points  for  the  expanded  rail  dine. 
Repeat  this  process  with  the  knuckle,  with  this  exception,  that  the 
corrected  knuckle  line  in  the  Half  Breadth  is  got  by  setting  forward 
of  G  A,  the  distances  lifted  from  the  Sheer.  The  level  lines,  etc., 
are  dotted  in. 

Join  together  the  frame  and  buttock  points  on  the  expanded  rail 
and  knuckle.  The  position  of  the  cant  frames  may  be  found  by 
placing  them  in  the  Half  Breadth  and  girthing  the  original  or  initial 
rail  and  knuckle  lines  for  the  same.  They  are  then  set  along  the 
expanded  lines.  The  butts  of  the  plating  are  fixed  to  clear  cants. 
Allowance  should  be  made  for  turning  down  on  to  the  fender. 


STERN   EXPANSION.  53 

of  the  cants  and  buttocks  lifted  and  girthed  round  the  expanded 
edge  they  should  agree  with  the  positions  already  indicated  when  the 
plan  is  correct.  The  butts  of  the  plating  are  now  arranged  clear  of 
the  cants  and  the  ordinary  frames,  and  a  skeleton  template  made 
showing  the  expanded  top  and  bottom  edges  with  cross  pieces  nailed 
on  for  the  heel  of  cants,  T,  and  I  frames,  with  the  set  line  marked 
across  them.  The  plater  extends  indefinitely  on  the  boards  the  line 
P  X  in  the  direction  of  X,  and  turns  the  template  over  to  find  the 
position  of  R1  on  the  line  for  the  reverse  side  of  the  vessel.  Allowance 
in  ordering  and  working  the  plates  should  be  made  on  the  top  and 
bottom  edges  for  connections.  The  plates  are  ordered  to  embrace  the 
curve,  and  care  should  be  exercised  to  see  that  the  plate  is  sufficiently 
wide  to  make  the  connections  at  top  and  bottom. 

Expansion  of  a  Tumble- home  Stern. — The  stern  in  small 
coasters,  tug-boats,  and  river  craft  is  sometimes  formed  as  shown  in 
Fig-.  47.  In  that  case  the  expansion  is  somewhat  different  to  that 
already  described.  Show  in  the  Sheer,  Half  Breadth,  and  Body,  the 
initial  faired-up  lines,  i.e.,  the  frames,  buttocks,  rail,  and  knuckle. 
Join  F  to  B  and  G  to  A.  Extent  indefinitely  A  B  to  C.  Erect  per- 
pendiculars or  set  lines  A  D  and  B  E  of  indefinite  length.  Through  points 
a,  b,  c,  d,  e,  f,  and  g  drop  perpendiculars  on  to  B  C,  and  draw  level  lines 
through  the  same  points  in  the  Half  Breadth,  a\  b\  c1,  d1,  etc.,  to  the 
rail  vertical.  Lift  in  the  Sheer  the  square  distance  of  the  points  a,  b, 
c,  d,  e,f,  and  g  from  B  C,  and  lay  them  off  forward  of  F  B  in  the  Half 
Breadth  on  their  respective  level  lines,  and  trace  the  dotted  line 
through  the  spots,  which  is  called  the  corrected  rail  line.  Girth  this 
line  from  the  centre  for  the  new  position  of  the  buttocks  and  frames, 
and  measure  the  distances  out  from  B  on  B  E,  and  from  the  points 
erect  perpendiculars  to  cut  the  lines,  produced,  already  shown 
through  a,  b,  e,  d,  etc.,  which  are  parallel  to  B  E.  The  intersection 
of  corresponding  lines  will  give  points  for  the  expanded  rail  -line. 
Repeat  this  process  with  the  knuckle,  with  this  exception,  that  the 
corrected  knuckle  line  in  the  Half  Breadth  is  got  by  setting  forward 
of  G  A,  the  distances  lifted  from  the  Sheer.  The  level  lines,  etc., 
are  dotted  in. 

Join  together  the  frame  and  buttock  points  on  the  expanded  rail 
and  knuckle.  The  position  of  the  cant  frames  may  be  found  by 
placing  them  in  the  Half  Breadth  and  girthing  the  original  or  initial 
rail  and  knuckle  lines  for  the  same.  They  are  then  set  along  the 
expanded  lines.  The  butts  of  the  plating  are  fixed  to  clear  cants. 
Allowance  should  be  made  for  turning  down  on  to  the  fender. 


54  NAVAL  ARCHITECTURE. 


CHAPTER  VI. 

Scrieve  Board  :  Information  placed  upon  it — Its  Purpose — How  Prepared — 
Scrieving  in  the  Frames— Decks — Shell  Plating  Sight  Edges— Shell 
Plating  Inner  Edges — Ribbands,  Keelsons,  Floors,  Cant  Knees — Lifting 
Beams— Frame  Bevels — Applying  Bevels — Checking  Bevels — Handy 
Bevelling  Machine — Machine  Bevelling. 


SCRIEVE  BOARD. 

The  Scrieve  Board  is  a  platform  formed  of  well-seasoned  deals,  laid 
edge  to  edge,  fastened  securely  together,  and  placed  in  position  near 
the  frame  furnace.  It  is  planed  on  the  top  side,  and  then  coated  with 
a  mixture  of  lamp  black  and  liquid  turpentine.  When  dry  the  Body 
plan  is  copied  upon  it,  and  the  lines  cut  in  with  a  "  scrieve-knife. 
Sometimes  both  sides  of  the  ship  are  scricved  in,  with  the  base  line  of 
each  body  on  opposite  edges,  so  that  the  frames  lap  unto  each  other, 
but  to  prevent  confusion  it  is  better  to  place  each  full  Body  on  separate 
boards,  or  only  to  scrieve  half  of  the  ship,  as  shown  in  Fig.  48. 

The  Information  placed  upon  it.—  The  moulded  shape  of  every 
frame,  floor,  and  tank  knee.  The  position  on  the  frames  of  all  decks, 
platforms,  shell  plate  edges,  keelsons,  ribbands,  harpins,  side  stringers 
and  girders,  keels,  stern  cants,  screw  boss,  number  of  each  frame,  and 
whatever  comes  in  contact  with  the  frames,  reverses,  or  floors. 

Its  purpose  is  that  every  frame,  reverse,  floor,  and  beam  may  be 
turned  by  the  platform  men  to  their  proper  shape,  and  punched  and 
marked  for  receiving  the  other  parts  of  the  structure. 

How  Prepared. — Strike  in  with  a  chalk  line  the  base  of  the 
after  body,  and  erect  with  trammels  a  perpendicular  to  it  for  the  centre 
line  on,  or  about,  the  middle  of  the  board.  Then  place  in  position 
lines  for  the  half  breadth,  depth  moulded,  rise  of  bottom,  half  siding 
of  stern  post,  level  or  water-lines,  buttocks,  and  diagonals.  Transfer 
on  a  short  batten  from  the  Sheer  on  the  loft  floor  heights  of  the  rail, 
knuckle  and  deck  at  side  above  the  depth  moulded  line  at  every  frame, 
and  strike  in  level  lines  through  the  spots  ;  the  after  sheers  over  the 
after  body,  and  the  forward  sheers  over  the  forward  body.  Then  lift 
from  the  Half  Breadth  the  half  beam  on  every  frame  at  rail,  knuckle 
and  deck,  and  place  them  on  their  corresponding  sheer  heights  just 
lined  in.     Do  the  same  with  the  J,  ordinates  on  the  level  lines  and  on 


Fig.  48. 


AQOa     3MOJ 


AFTER     BODY 


SCRIEVE  BOARD.  55 

the  diagonals  ;  also  lift  from  the  Sheer  above  the  base  the  points  of 
intersection  of  the  frames  and  buttocks,  and  the  height  of  the  after 
frame  feet  on  the  inside  of  the  stern  post,  and  transfer  them  unto  the 
board  on  the  buttocks  and  the  half  siding  of  the  post  respectively. 
Where  the  spots  come  very  close,  it  is  usual  only  to  lift  every  rifth 
frame  and  divide  the  others  in  suitably  by  inspection.  The  points 
are  marked  on  the  scrieve  board  with  a  sharp-pointed  loft  nail,  and 
afterwards  chalked  in  and  numbered  for  clearness. 

Scrieving  in  the  Frames. — Pin  a  suitable  batten — thick  at 
the  ends  and  thin  about  the  middle  for  the  bilge  curve — to  the  mid- 
ship frame  spots;  fair  it  carefully  and  scrieve  in.  With  this  as  a  guide, 
in  conjunction  with  spots,  French  chalk  in  fair  for  about  quarter 
length  amidships  every  fifth  frame.  The  intermediates  being  close 
are  divided  in  on  a  graduated  scale— this  is  frequently  done  on  a  short 
batten — then  the  scrieving  in  of  every  frame  from  the  midships  is  pro- 
ceeded with.  When  the  after  body  is  scrieved,  a  base  line  for  the  fore 
Body  is  lined  in  on  the  opposite  edge  of  the  board,  in  such  a  position 
that  some  of  the  level  lines  of  the  after  Body  extended  across  will  work 
in.  The  centre  line  is  kept  away  from  that  of  the  after  Body  which 
allows  the  reversing  spots  of  the  after  Body  to  be  marked  clearly  over 
the  fore  Body  as  shown.  The  initial  lines,  as  in  the  after  Body,  are 
placed  in  position,  and  the  midship  section  copied  from  the  after 
Body  by  making  a  wood  template  of  the  form.  The  spots  for  the 
water-lines,  diagonals,  bow  lines,  sheer  heights,  and  frame  feet  are 
lifted  from  the  loft  floor,  and  set  off  on  the  scrieve  board,  and  the 
process  carried  out  as  in  the  after  Body. 

The  frames  are  usually  first  scrieved  in  without  regard  to  the 
position  of  the  screw  boss  or  bosses,  or  any  projection,  and  the  altera- 
tion set  forth  on  page  12  for  the  boss  carried  out. 

Many  of  the  shipbuilders  lay  off  their  vessels,  in  the  office,  on  f 
inch  scale,  on  the  diagonal  system,  and  supply  the  loftsman  with 
ordinates  on  these  diagonals,  which  are  shown  in  Fig-.  49.  In  that 
case  the  positions  of  the  diagonals  up  the  centre,  on  the  base,  and  on 
the  half  moulded  breadth  line  are  given  the  loft  with  the  ordinates 
on  the  run  of  the  diagonals,  instead  of  the  level  line  half  ordinates. 

In  other  yards  the  ship  is  laid  down  on  $  inch  scale,  in  the  office, 
as  described  in  Chapter  I.,  and  ordinates  and  particulars  supplied  lofts- 
man in  a  book  from  this  plan  for  "scrieving  ship  in."  The  after  end, 
for  a  distance  of  about  20  feet  forward  of  the  transom,  being  faired-up 
full  size  on  the  loft  floor  at  the  same  time  as  the  stern.     It  is  not  our 


'LIBRA/fj 


THE 


OF  CAL\»0^* 


SCRIEVE  BOARD.  55 

the  diagonals  ;  also  lift  from  the  Sheer  above  the  base  the  points  of 
intersection  of  the  frames  and  buttocks,  and  the  height  of  the  after 
frame  feet  on  the  inside  of  the  stern  post,  and  transfer  them  unto  the 
board  on  the  buttocks  and  the  half  siding  of  the  post  respectively. 
Where  the  spots  come  very  close,  it  is  usual  only  to  lift  every  fifth 
frame  and  divide  the  others  in  suitably  by  inspection.  The  points 
are  marked  on  the  scrieve  board  with  a  sharp-pointed  loft  nail,  and 
afterwards  chalked  in  and  numbered  for  clearness. 

Scrieving  in  the  Frames. — Pin  a  suitable  batten — thick  at 
the  ends  and  thin  about  the  middle  for  the  bilge  curve — to  the  mid- 
ship frame  spots;  fair  it  carefully  and  scrieve  in.  "With  this  as  a  guide, 
in  conjunction  with  spots,  French  chalk  in  fair  for  about  quarter 
length  amidships  every  fifth  frame.  The  intermediates  being  close 
are  divided  in  on  a  graduated  scale— this  is  frequently  done  on  a  short 
batten — then  the  scrieving  in  of  every  frame  from  the  midships  is  pro- 
ceeded with.  When  the  after  body  is  scrieved,  a  base  line  for  the  fore 
Body  is  lined  in  on  the  opposite  edge  of  the  board,  in  such  a  position 
that  some  of  the  level  lines  of  the  after  Body  extended  across  will  work 
in.  The  centre  line  is  kept  away  from  that  of  the  after  Body  which 
allows  the  reversing  spots  of  the  after  Body  to  be  marked  clearly  over 
the  fore  Body  as  shown.  The  initial  lines,  as  in  the  after  Body,  are 
placed  in  position,  and  the  midship  section  copied  from  the  after 
Body  by  making  a  wood  template  of  the  form.  The  spots  for  the 
water-lines,  diagonals,  bow  lines,  sheer  heights,  and  frame  feet  are 
lifted  from  the  loft  floor,  and  set  off  on  the  scrieve  board,  and  the 
process  carried  out  as  in  the  after  Body. 

The  frames  are  usually  first  scrieved  in  without  regard  to  the 
position  of  the  screw  boss  or  bosses,  or  any  projection,  and  the  altera- 
tion set  forth  on  page  12  for  the  boss  carried  out. 

Many  of  the  shipbuilders  lay  off  their  vessels,  in  the  office,  on  f 
inch  scale,  on  the  diagonal  system,  and  supply  the  loftsman  with 
ordinates  on  these  diagonals,  which  are  shown  in  Fig.  49.  In  that 
case  the  positions  of  the  diagonals  up  the  centre,  on  the  base,  and  on 
the  half  moulded  breadth  line  are  given  the  loft  with  the  ordinates 
on  the  run  of  the  diagonals,  instead  of  the  level  line  half  ordinates. 

In  other  yards  the  ship  is  laid  down  on  %  inch  scale,  in  the  office, 
as  described  in  Chapter  I.,  and  ordinates  and  particulars  supplied  lofts- 
man in  a  book  from  this  plan  for  "scrieving  ship  in."  The  after  end, 
for  a  distance  of  about  20  feet  forward  of  the  transom,  being  faired-up 
fuU  size  on  the  loft  floor  at  the  same  time  as  the  stern.     It  is  not  our 


56 


NAVAL  ARCHITECTURE. 


desire  to  express  any  opinion  respecting  the  merits  of  the  various 
systems  ;  they  have  been  found  to  answer  the  purpose  effectually,  or 
they  would  not  be  continued. 

Fig.  49. 


AFTER    BODY 


•  Scrieving  in  the  Deck  Lines, — The  upper  deck  sheer  at  side 
above  the  depth  moulded  line,  on  about  every  fifth  frame,  is  lifted 
from  the  loft  floor  on  a  batten,  and  transferred  on  to  the  respective 
frames  on  the  scrieve  board,  and  the  line  scrieved  in.  The  main  and 
lower  deck  side  lines  are,  sometimes,  made  parallel  to  this  line,  which 


SCRIEVE  BOARD.  57 

means  that  the  centre  'tween  deck  height  is  a  variable  quantity 
and  open  to  objection.  A  better  plan  is  to  make  all  the  decks  with 
camber  parallel  to  one  another  at  all  points.  This  may  be  done  by 
placing  the  upper  edge  of  the  beam  camber  mould  fair  with  the  mid- 
ship side  line,  and  its  centre  on  that  of  the  Body ;  and  setting  the 
centre  of  a  duplicate  mould  fair  with  that  of  the  ship  and  its  top 
edge  parallel  to  the  top  edge  of  the  first  mould  and  at  a  suitable 
distance  down,  i.e.,  height  'tween  decks  ;  mark  the  point  where  the 
second  mould  cuts  the  midship  frame.  Then  lift  on  a  batten  the  per- 
pendicular heights  from  the  upper  mould  edge  to  the  deck  line,  and 
set  them  off,  on  their  respective  frames,  parallel  to  the  centre  above 
the  second  mould  edge,  which  will  give  points  for  the  main  deck  line. 
Repeat  the  process  for  the  lower  and  other  decks,  if  cambered. 

Fig.  49  shows,  perhaps,  an  easier  method  of  doing  this.  Let  A  B 
be  the  side  line  of  the  upper  deck.  Then  set  off  camber  lines — due 
to  width  of  the  ship  at  the  deck — a,  b,  c,  on  the  midship  frame  at 
each  deck,  which  may  be  done  with  the  beam  mould.  Lift  on  a 
batten,  for  frames  6,  12,  and  30,  de,fg,  hi  above  camber  line  a  of  the 
upper  deck,  and  place  the  distances  on  their  corresponding  frames 
above  the  camber  line  b  of  the  main  deck,  d1  e1,  fxgl,  hlil  re- 
spectively. Draw  curve  through  the  spots  and  you  have  main  deck 
side-line,  which  fair-up  and  scrieve  in.  Repeat  the  process  at  the 
lower  deck  if  necessary.  The  fore  body  deck  lines  are  formed  in  the 
same  way. 

Scrieving  in  the  Shell  Plating  Sight  Edges. — The  width 
of  each  strake  on  the  midship  frame,  with  the  breadth  of  the  edge  laps, 
and  the  distance  above  the  deck  of  the  sheer  strakes,  together  with 
a  tracing  showing  the  run  of  the  plate  edges  is  usually  given  to  the 
loftsman.  The  midship  widths  he  places  around  the  midship  section 
as  near  as  possible.  The  sheer  and  garboard  strakes,  and  the  flat  keel 
plate  admit  of  no  alteration  and  are  carried,  if  possible,  forward  and 
aft  about  the  same  width.  Any  addition  or  lessening  of  the  widths 
must  be  made  on  the  thin  strakes.  To  get  the  curve  of  the  sight 
edges  for  the  scrieve  board,  straight  lines  a  b,  c  d,  ef,  g  h,  in  Fig.  40, 
are  drawn  across  the  ^  inch  scale  body  sections  from  the  plate  sight 
edge  on  the  midship  section  to  the  centre  line  ;  and  the  distance  of 
the  plate  edge  of  each  strake  is  girthed  on  the  sections  from  this 
line,  and  on  the  copy  given  to  the  loftsman  these  dimensions  and  lines 
are  marked  ;  so  that  it  is  an  easy  matter  to  mark  off  the  lines  on  the 
scrieve  board  and   set   therefrom   the   position   of   the   plate  edges. 


58  NAVAL  ARCHITECTURE. 

Amidships,  the  points  may  require  a  little  manipulation  to  suit  the 
correct  sheer,  which,  in  most  cases,  will  not  agree  exactly  with  the 
I  inch  scale  Sheer  Draught.  After  this  is  done,  the  lines  are  faired- 
up  and  scrieved  in.  Care  should  be  taken  that  the  (girthed)  width 
of  the  boss  or  furnace  plate  is  not  too  wide  for  the  furnace.  Many 
of  the  shipbuilders  give  the  loftsman  the  girthed  widths  of  the  sight 
edges  on  about  every  fifth  section,  with  heights  on  the  posts,  which 
are  set  round  the  scrieve  board  frames,  and  after  fairing  are  scrieved  in. 

Scrieving  in  the  Extreme  Edges  of  the  Inside  Strakes. — 
This  is  easily  done  by  girthing  round  the  frames  from  the  sight  edges 
the  width  of  the  lap  and  scrieving  a  line  through  the  spots  in  each 
case.  The  lines  are  shown  dotted  in  Fig.  48  to  distinguish  them ;  the 
usual  practice  is  to  paint  the  lap  in. 

Scrieving  in  the  Ribbands. — They  are  arranged,  as  in  Fig. 
48,  on  the  outside  strakes  clear  of  the  decks  and  inside  strakes,  if 
possible,  for  the  entire  length— marked  1  R,  2  R,  3  R,  etc. 

Scrieving  in  the  Side  Keelsons. — In  a  ship  with  turned-up 
floors  the  curved  line  will  commence  from  the  top  edge  of  the  floor 
where  the  intercostal  cuts.  Those  clear  of  a  double  bottom  from  the 
moulded  edge  of  the  frame ;  except  in  the  case  of  a  keelson  not  extend- 
ing to  the  shell  plating,  then  the  width  of  the  frame  must  be  set  in  for 
the  starting  point  of  the  curved  line. 

Scrieving  in  the  Cant  Frame  Knees. — The  moulded  edge  of 
the  vertical  bar  attaching  knees  to  the  transom  floor  is  scrieved  in, 
shown  by  marks  1  C,  2  C,  3  C,  etc.,  in  Fig.  48.  The  positions  are 
lifted  on  the  run  of  the  transom  from  the  Half  Breadth  on  the  loft 
floor.  * 

It  remains  to  add  that  whatever  has  to  be  attached  to  the  frames, 
reverses,  or  floors,  must  be  distinctly  shown  on  the  scrieve  board. 
This  will  decide  any  doubtful  point. 

In  the  sketch,  Fig.  48,  to  make  it  clear,  only  occasional  frames 
are  shown,  but  every  frame,  floor,  etc.,  must  be  scrieved-in  in  an 
actual  case. 

Scrieving  in  the  Floors. — In  a  ship  with  1 11  met  I  up  floors 
they  are  simply  copied  from  the  Body  sections,  which  is  fully  explained 
on  page  37,  the  intermediates  being  either  divided  in  or  lifted  on 
each  buttock  from  the  faired  longitudinal  lines  and  scrieved  in.  In 
cases  where  the  floors  are  ordered  in  a  hurry  from  a  small  scale  plan 

*In  battle-ships  the  side  armour,  and  backing  lines,  together  with  longi- 
tudinal bulkheads,  are  scrieved  in  on  the  boards. 


Fig.  50. 
AFTER    BODY 


BEAM    MOULD 


FORE    BODY 


- — •       ^ 

I                     IbS 

-171                 T" 

■Jfi2           /  _ 

\                   15& 

1 

\              "H 

i^o             / 

1  A 

j\ 

,,       ~1 
1   11         ' 

t3                122. 

JSB  '             / 
_L£6            N| 

I  6 

1 

4      o 

1 

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BEAM     MOULD 


Him 


SCRIEVE  BOARD.  59 

before  the  ship  is  laid  off  properly  (or  very  much  decided),  it  is  best  to 
carry  out  on  the  scrieve  board  the  method  described  on  page  38, 
and  check  the  ordered  sizes  of  the  plates  to  prevent  unnecessary  delay. 
The  loftsman,  therefore,  is  supplied  with  a  copy  of  the  ordered  floor 
specification.  When  a  cellular  double  bottom  is  fitted  in  a  merchant 
ship  the  floor  top  is  usually  level  right  fore  and  aft.  In  flat  bottomed 
ships  it  may  be  cambered  slightly  to  allow  the  floors  to  be  ordered  as 
sketches  under  9  inches  taper.  The  inner  bottom  being  flat  it  is 
chalked  in  parallel  to  the  base  line,  and  on  it  is  set  off  for  each  frame 
the  knuckle  points.  The  cutting  line  on  the  frames  is  transferred 
on  to  the  boards,  and  a  curve  passed  through  the  spots.  The  knuckle 
and  frame  points  of  the  side  are  connected,  and  care  taken  that 
these  lines  are  square  to  the  frame  surface  in  each  case.  When 
chalked  in  they  are  faired  on  the  loft  floor  in  the  manner  described 
on  page  41,  and  then  scrieved.  The  knees  outside  of  the  double 
bottom  are  next  placed  in  position.  For  this  purpose  strike  in 
the  "diminishing  line,"  as  explained  on  page  44,  on  which  all  the 
knees  terminate  at  the  frame ;  and  join  knuckle  point  of  the  tank  side 
with  corresponding  frame  on  this  diminishing  line.*  The  side  girders 
in  the  double  bottom  are  placed  in  position  clear  of  the  shell  plate 
edges  and  made  parallel  to  the  centre  line  in  merchant  ships.  Extra 
girders  are  usually  fitted  in  the  engine  space.  The  entire  double 
bottom  is  then  scrieved.  For  the  purposes  of  testing  frames,  etc., 
their  position  on  level  and  diagonal  lines  are  shown  on  the  opposite 
side,  together  with  the  tank  side  and  knees  (see  Fig.  48).  In  the  case 
of  the  cellular  double  bottom  of  a  war  vessel,  great  care  is  taken  in 
fairing-up  the  inner  bottom  and  longitudinals  on  the  loft  floor,  so 
that  it  only  becomes  necessary  to  copy  the  body  plan  on  to  the  scrieve 
board.     The  system  of  fairing  is  described  on  page  130. 

Lifting  the  Length  of  the  Beams. — The  loftsman  is  supplied 
with  a  list  of  the  beam  frames  on  each  deck.  These  he  marks 
distinctly  with  chalk  on  the  scrieve  board  for  a  short  distance  below 
and  above  the  deck  line.  One  mould  may  be  made  to  serve  the 
purpose  of  each  deck,  if  the  different  bodies  are  put  on  reverse  sides 
of  the  mould.  The  method  of  lifting  is  to  place  the  mould  centre  in 
Fig.  50  fair  with  the  centre  line  of  the  scrieve  board  and  touching 
the  deck  line,  at  each  side,  on  the  midship  frame.  Then  lift  on  a  lath 
square  up  from  the  edge  of  the  mould  the  distance  of  the  deck  line 
on  the  beam  frames,  like  A,  B,  C,  and  D,  and  set  these  distances  off 

*  The  height  of  knee  at  the  knuckle  may  be  slightly  below  the  inner  bottom. 


tfSfc  L,E 


OF  IBB 


•QNIVERSIT^ 


SCRIEVE  BOARD.  59 

before  the  ship  is  laid  off  properly  (or  very  much  decided),  it  is  best  to 
carry  out  011  the  scrieve  board  the  method  described  on  page  38, 
and  check  the  ordered  sizes  of  the  plates  to  prevent  unnecessary  delay. 
The  loftsman,  therefore,  is  supplied  with  a  copy  of  the  ordered  floor 
specification.  When  a  cellular  double  bottom  is  fitted  in  a  merchant 
ship  the  floor  top  is  usually  level  right  fore  and  aft.  In  flat  bottomed 
ships  it  may  be  cambered  slightly  to  allow  the  floors  to  be  ordered  as 
sketches  under  9  inches  taper.  The  inner  bottom  being  flat  it  is 
chalked  in  parallel  to  the  base  line,  and  on  it  is  set  off  for  each  frame 
the  knuckle  points.  The  cutting  line  on  the  frames  is  transferred 
on  to  the  boards,  and  a  curve  passed  through  the  spots.  The  knuckle 
and  frame  points  of  the  side  are  connected,  and  care  taken  that 
these  lines  are  square  to  the  frame  surface  in  each  case.  When 
chalked  in  they  are  faired  on  the  loft  floor  in  the  manner  described 
on  page  41,  and  then  scrieved.  The  knees  outside  of  the  double 
bottom  are  next  placed  in  position.  For  this  purpose  strike  in 
the  "diminishing  line,"  as  explained  on  page  44,  on  which  all  the 
knees  terminate  at  the  frame ;  and  join  knuckle  point  of  the  tank  side 
with  corresponding  frame  on  this  diminishing  line.*  The  side  girders 
in  the  double  bottom  are  placed  in  position  clear  of  the  shell  plate 
edges  and  made  parallel  to  the  centre  line  in  merchant  ships.  Extra 
girders  are  usually  fitted  in  the  engine  space.  The  entire  double 
bottom  is  then  scrieved.  For  the  purposes  of  testing  frames,  etc., 
their  position  on  level  and  diagonal  lines  are  shown  on  the  opposite 
side,  together  with  the  tank  side  and  knees  (see  Fig.  48).  In  the  case 
of  the  cellular  double  bottom  of  a  war  vessel,  great  care  is  taken  in 
fairing-up  the  inner  bottom  and  longitudinals  on  the  loft  floor,  so 
that  it  only  becomes  necessary  to  copy  the  body  plan  on  to  the  scrieve 
board.     The  system  of  fairing  is  described  on  page  130. 

Lifting  the  Length  of  the  Beams. — The  loftsman  is  supplied 
with  a  list  of  the  beam  frames  on  each  deck.  These  he  marks 
distinctly  with  chalk  on  the  scrieve  board  for  a  short  distance  below 
and  above  the  deck  line.  One  mould  may  be  made  to  serve  the 
purpose  of  each  deck,  if  the  different  bodies  are  put  on  reverse  sides 
of  the  mould.  The  method  of  lifting  is  to  place  the  mould  centre  in 
Fig.  50  fair  with  the  centre  line  of  the  scrieve  board  and  touching 
the  deck  line,  at  each  side,  on  the  midship  frame.  Then  lift  on  a  lath 
square  up  from  the  edge  of  the  mould  the  distance  of  the  deck  line 
on  the  beam  frames,  like  A,  B,  C,  and  D,  and  set  these  distances  off 

*  The  height  of  knee  at  the  knuckle  may  be  slightly  below  the  inner  bottom. 


60 


NAVAL  ARCHITECTURE. 


on  the  centre  line  above  the  edge  of  the  mould  and  number  the 
points.  Then  scrieve  the  form  of  the  midship  frame,  for  the  port  and 
starboard  sides,  on  the  mould  ;  setting  in  the  line  about  |  of  an  inch 
owing  to  the  beam  arm  having  to  go  into  the  bosom  of  the  frame. 
There  are  cases  where  the  beams  are  on  the  heel  of  the  frames.  Then 
shift  the  mould  up  to  the  next  beam  frame  at  the  deck  line,  keeping 

Fig.  51. 

AFTER    BODY 


the  centre  right,  and  mark  it  in  the  same  manner.  This  process  is 
repeated  until  all  the  beams  of  each  body  are  scrieved  on  the  mould 
to  the  form  of  the  frames.  In  Fig.  50  the  mould  is  shown  dotted  in 
position  when  lifting  numbers  6  and  162.  The  centre  heights  are  not 
necessary  when  both  sides  of  the  ship  are  scrieved,  but  if  only  half  of 
the  body  is  shown  they  are  indispensable  ;  the  mould  must  be  carefully 
placed  on  the  midship   frame  before  lifting   the  heights,  i.e.,  level 


SCRIEVE  BOARD. 


61 


across  and  centred.  After  scrieving  one  side,  the  scrieve  is  reversed 
with  care  to  the  other  side,  by  bending  a  lath  round  the  edge  of  the 
mould  and  transferring  the  spots.  The  form  of  the  frame  from  these 
points  is  got  by  an  adjustable  set  square  marked  E,  and  by  noting  the 
amount  of  round  on  the  frame.  The  beams  are  then  numbered,  and  the 
ship's  number  and  the  name  of  the  deck  scrieved  in.  When  an  iron 
deck  has  to  be  fitted  the  laps  of  the  plating  are  marked  on  the  edge 

Fig.   52. 


FRAME  BEVELS.     No.                  SHIP. 

No.  of 
Frame. 

BEVELS  IN  INCHES. 

1 

2 

3 

1 
4           5 

6          7          8 

9 

10 

ii 

12 

Transom. 

19      14* 

94 

6* 

6 

8* 

1 

18| 

14* 

10| 

n 

6* 

3| 

2 

19|    19£ 

15 

lOf 

H 

61 

4* 

3 

22^-    20*    17 

12 

H 

6* 

5^ 

4 

21i 

21      18| 

16i 

12* 

H 

8* 

4 

5 

6 

7 

8 

9 

10 

11 

12 

1 

of  the  mould.  In  some  cases  for  a  wood  deck  the  widths  of  the 
planks  are  supplied,  which  being  marked  on  a  lath  are  given  to  beam- 
turner  to  punch  horizontal  flange  of  the  beam.  Each  beam  is  set 
in  the  squeezes  to  the  shape  of  this  mould. 

The  holes  for  the  beam  arms  are  marked  from  a  duplicate  template 
used  on  the  boards  for  punching  the  frames,  so  that  the  beam  and 
frame  correspond. 

All  beams  are  not  cambered  ;  in  the  case  of  wide  spaced  hold 
beams  they  act  structurely  more  to  the  purpose  of  strength  by  being 
straight  across  the  ship.     In  the  case  of  web  frames  the  beam  arm 


62 


NAVAL  ARCHITECTURE. 


Fig.   53. 


N°l  FRA^£ 


mffimi 


will  stand  in  from  the  heel  of  the  frame  more  than 
|  of  an  inch  ;  in  certain  classes  of  web  frame  beams 
the  beam  is  attached  to  the  frame.  Perhaps  the  wisest 
plan  is  to  give  a  separate  mould  for  the  web  frame 
beams. 

A  separate  camber  mould,  with  only  the  centre  line 
marked  on,  is  given  for  bulkheads.  A  lath,  showing 
the  length  of  the  beams,  is  also  sometimes  given  out 
with  the  moulds  by  the  loftsman. 

Lifting  the  Bevels  of  the  Frames  from  the 
Scrieve  Board. — Where  the  work  of  bevelling  the 
bars  is  done  by  manual  labour  the  bevels  are  taken 
at  each  plate  edge,  or  at  the  ribbands.  Fig.  51 
shows  an  enlarged  sketch  of  a  few  frames  in  the  after 
body.  Lift  the  distance,  as  shown,  between  consecu- 
tive scrieves,  square  off  from  the  frame  you  are  dealing 
with,  and  enter  them  on  a  sheet  of  paper,  or  in  a  book 
(see  Fig.  52).  A  few  bevel  boards  are  made  of  soft 
wood,  like  Fig.  53,  4  to  5  feet  long,  and  of  the  width 
of  the  frame  shell  flange.  In  Fig.  54  is  given  a  sketch 
of  a  wood  machine  for  marking  the  bevels  on  the  board. 
The  different  spacing  of  frames,  from  20  to  2G  inches, 
is  lined  on  the  centre  line  of  the  machine,  measured 
from  A.  The  screw  B  is  fixed  on  the  centre  through 
the  groove  in  the  movable  leg  M  to  the  fore  and  aft 
spacing  of  the  frames  from  heel  to  heel  of  bars.  A 
scale  of  inches  is  marked  along  the  bottom  piece  to 
take  all  possible  distances  between  the  scrieves.  This 
scale  is  only  on  the  right-hand  side  of  the  centre, 
because  the  bevel  must  always  be  standing  or  open. 
The  bevel  board  is  placed  in  position,  as  shown,  behind 
M,  and  the  front  edge  of  the  leg  M  is  moved  to  the 
distance  between  the  scrieves  given  in  Fig.  52,  and  a 
line  drawn  across  the  board  and  numbered :  this  mark- 
gives  the  distance  the  bar  has  to  be  opened  from  the 
heel  to  the  top,  or  the  angle  of  opening  (see  "  a  "  in 
small  Fig.  55).  The  process  is  repeated  until  both 
sides  of  the  board  are  filled  with  bevels  (given  in 
Fig.  53),  when  other  boards  are  secured  and  filled 
until  all  the  frames  are  lifted. 


SCRIEVE  BOARD. 


63 


Applying  the  Bevels  to  the  Frame  Bars.— Lift  the  bevel 
from  the  board  by  an  adjustable  set  square  in  the  manner  shown  in 
the  Fig.  53,  and  apply  it  when  bevelling  square  to  the  heel  or  back  of 
the  bar  when  it  is  lying  on  the  bending  slab  (as  shown  in  Fig.  55 ) 
with  the  arm  B  laid  on  the  slab. 

Fig.  54. 


FRONT   VIEW 


f 


.GROOVE 


,SCREW 


Fig.  55. 

Vi 

\\  .FRAME  BAR 

\ 

"bt&zzmm amaiNC  slab 


DISTANCE    BETWEEN     SCRIEVES  IN  INCHES 


Checking  the  Frame  Bar  Bevels  on  the  Boards.— A  light 
iron  skeleton  machine  (Fig.  56),  sometimes  called  the  "detective,"  is 
used  for  this  purpose.  The  frame  bar  is  placed  on  the  scrieve  line 
and  the  machine,  fixed  to  the  correct  spacing  of  the  frames,  is  made  to 
stand  square,  off  to  the  bar,  with  the  point  A  on  the  next  scrieve. 
Then  the  front  edge  of  the  movable  leg,  with  its  point  at  the  heel  of 
the  frame,  should  touch  for  the  full  depth  of  the  flange  if  the  bevel  is 
correct.     All  frames  are  tested  in  this  way  before  erection. 


64 


NAVAL  AKCHITECTUEE. 


Handy  Bevelling-  Machine. — Fig-.  57  shows  another  bevelling 
machine  made,  to  £  full  size,  of  hard  wood.  A  narrow  brass  plate  A  is 
fixed  along  the  edge  in  winch  holes  are  bored  and  tapped  for  fixing  the 


Fig.  56. 


SECTION 


screw  D  to  the  correct  spacing  of  the  frames.     On  the  edge  B  C  is  set 


off  inches  and  parts  of  an  inch, 
one  already  described. 


It  is  used  in  the  same  manner  as  the 


SCRIEVE  BOARD. 


65 


Machine  Bevelling. — Most  of  the  large  shipbuilding  establish- 
ments have  bevelling  machines,  standing  in  front  of  the  furnace,  for 
bevelling  the  bar  as  it  is  drawn  out  of  the  furnace.  The  bevels  for 
this  purpose  must  be  in  degrees  of  a  circle.     These  are  got  by  applying 

Fig.   57. 

END   VIEW 


"*       ill 


MOVEABLE     LEG 


BEVEL        50ARD 


BRASS    SLIP  A 


to  the  lines  on  the  bevelling  board  a  quadrant  with  a  projecting  ledge, 
and  obtaining  the  degrees  you  mark  them  with  chalk  on  the  dial  placed 
on  the  front  of  the  bevelling  machine.  Fig.  58  shows  the  quadrant 
set  on  the  board  to  bevel  7,  which  is  20|  degrees.  It  is  only 
necessary  to  say  that  the  bevels  are  taken  at  uniform  distances  apart, 
usually  4  to  5  feet,  beginning  at  the  deck  or  centre,  whichever  is 
most  convenient. 


Fig.  58. 


QUADRANT 


BEVEL         BOARD 
N2  SHIP 


QUADRANT 


BIBBANDS  AND  HAEPINS.  07 


CHAPTER  VII. 

Ribbands:  Form  of  a  Ribband  Line — Stem  Termination— Stern  Termination 
— Laying  Ribband  Lines  Off  and  Marking  Battens — Deck  and  Inner 
Bottom  Ribbands.  The  Common  Hatpin:  Form  of  the  Moulded  Edge 
— Form  of  the  Bevelled  Edge — Bevelling  Board.  The  Sheer  Harpin  : 
Form  of  the  Moulded  Edge— Form  of  the  Bevelled  Edge— Bevelling 
Board — Expansion  of  Moulded  Edge  in  the  Sheer.  The  Stern,  Harpin  : 
Form  of  the  Moulded  Edge  -Form  of  the  Bevelled  Edge. 


RIBBANDS  AND  HARPINS. 

For  erecting  purposes,  to  keep  the  frames  in  their  relative  positions 
until  the  inside  strakes  of  the  shell-plating  are  in  place  and  secured, 
ribbands  and  harpins  are  used.  The  former,  which  are  made  of  pine 
wood  about  6  inches  siding,  are  placed  over  the  entire  length  of  the 
ship  on  the  outside  of  the  frames,  in  way  of  the  outside  strakes  of  the 
shell-plating.  They  are  usually  straight  lines  in  the  after  Body  sec- 
tions, and  curved  to  the  sheer  in  the  fore  Body  for  about  the 
half  length,  then  run  in  straight  to  the  stem.  The  line  placed  on 
the  scrieve  board  is  the  top  edge  of  the  ribband.  Where  the  vessel  is 
bluff  at  the  ends,  and  it  would  be  difficult  to  bend  the  ribband  to  the 
form  of  the  frames,  harpins  made  of  angle  bar  are  turned  to  the  ex- 
panded shape.  There  are  three  kinds  of  harpins  :  first,  the  common 
harpin,  which  appears  straight  in  the  Body  plan,  the  same  as  a  ribband ; 
second,  the  sheer  harpin,  which  takes  the  sheer  of  the  top  sides,  and, 
of  course,  appears  curved  in  all  the  plans ;  third,  the  stern  harpin, 
which  is  level  in  the  Body  and  Sheer  plans. 

The  True  Form  of  a  Ribband  Line.— It  is  found  by  bending 
a  light  lath  round  the  ribband  line  on  the  scrieve  board,  or  the  Body  on 
the  loft  floor,  and  girthing  relative  to  the  centre  line,  the  position  of 
the  half  siding  of  the  stem  and  stern  posts,  and  the  first  ten  frames  at 
the  ends;  afterwards,  about  every  fifth  will  answer  the  purpose.  Lay 
these  distances  off  on  the  loft  floor,  in  the  manner  to  be  hereafter 
described. 

To  Find  the  Termination  on  the  Stem. — Lift  the  position  of 
the  ribbands  on  the  scrieve  board  from  the  base  line  on  the  stem  half- 
siding  line,  and  set  the  heights  square  up  on  the  inside  of  the  stem  in 
the  Sheer  on  the  loft  floor.     Square  these  points  down  on  to  the  Half 


68  NAVAL  ARCHITECTURE. 

Breadth  centre  line,  and  place  on  these  perpendiculars  the  girthed 
board  width  from  the  centre  to  the  half-siding  in  each  case,  which 
give  the  terminations  of  the  ribbands  at  the  fore  end. 

To  Find  the  Termination  Aft. — When  the  ribband  lines  are 
below  the  foot  of  the  transom,  the  same  process  described  for  forward 
is  adopted ;  but  should  the  ribband  cut  the  transom  frame,  then  lift 
the  distance  of  the  point  square  out  from  the  centre  line,  and  lay  it 
out  on  the  same  frame  in  the  Half  Breadth  on  the  loft  floor.  This  is 
the  termination  on  the  transom  ;  the  other  points  will  be  got  by 
marking  on  a  lath  this  distance  and  -  swinging  the  lath  round — keep 
this  point  fair  on  the  transom  of  the  scrieve  board,  and  proceed  to  girth 
the  position  of  the  frames  forward  on  the  run  of  the  line  in  the 
usual  way. 

Laying  the  Ribband  Lines  Off  and  Marking  the  Ribband 
Battens. — The  girthed  distances,  lifted  from  the  scrieve  board,  are 
set  off  in  the  Half  Breadth  on  the  loft  floor  on  their  respective  frames, 
and  a  ribband  batten,  about  40  feet  long  by  if  inches  square,  made  of 
soft  pine,  is  bent  round  the  spots,  and  when  secured,  the  position  and 
number  of  every  frame  is  marked  upon  it  with  a  joiner's  soft  pencil. 
Care  should  be  taken  to  get  the  marks  square  to  the  edge  of  the  batten, 
so  that  either  edge  can  be  used  for  marking  off.  When  it  is  filled  on 
one  side,  turn  it  over  to  another,  and  mark  in  like  manner  by  a  con- 
tinuation of  the  ribband  line,  until  the  relative  position  of  the  frames 
on  the  run  of  the  line  right  fore  and  aft  are  lifted.  One  batten  is 
usually  sufficient  for  a  ribband,  which  has  its  number,  and  the 
ship's  number,  marked  upon  it.  The  process  is  repeated  for  each 
ribband  line ;  and  when  the  entire  lot  is  completed,  they  are  given  to 
the  shipwrights,  who  mark  on  the  top  side  of  the  ribbands  the  posi- 
tion of  each  frame.  Sometimes  they  are  scrieved  in.  Holes  are  bored 
in  the  ribbands  for  bolt  attachment  to  the  frames,  and  they  are  hoisted 
into  the  position  marked  on  the  frames  by  the  frame-turner  (the  two 
marks  being  brought  together),  and  well  secured  :  where  they  remain  to 
keep  the  ship  in  shape  until  the  inside  shell-plating  is  attached. 

N.B. — The  above  is  the  ordinary  way  of  lifting  the  position  of  the 
ribbands ;  but  it  is  more  correct  at  the  ends,  when  the  form  of  the 
ribband  is  placed  on  the  loft  floor,  to  set  out  from  the  line  half  the 
width  of  the  ribband,  and  bend  the  ribband  battens  round  these  spots 
for  the  true  length  and  position  of  the  frames. 

Deck  and  Inner  Bottom  Ribbands. — Ribbands  are  also  fitted 
on  the  upper  decks  and  inner  bottom  to  keep  the  decks  and  bottom  in- 


RIBBANDS  AND  HARPINS. 


69 


form  until  part  of  the  plating  is  attached.  Those  for  the  tank  sides 
may  be  lifted  from  the  loft  floor,  but  it  is  not  usually  done.  It  may 
be  noted  here  that  the  bevels  for  the  tank  side  bars  may  be  lifted 
from  the  scrieve  board  in  the  ordinary  way  ;  which  does  away  with 
the  practice  of  bending  a  ribband  round  tank  side  in  the  ship. 

Fig.   59. 


COMMON   HARPIN 


BODY 


SHEER 


Fig.  60. 

HARPIN  BAR 


Fig.  61. 


^  P- BEVEL 

ADJUSTABLE  SET  ifl       DAD 

SQUARE-.        'L BAR 

PLATFORM  -\-,^ 


Fig.   62. 


The  Common  Harpin  is  a  continuation  of  an  ordinary  ribband, 
its  purpose  and  form  being  the  same  ;  only  it  is  made  of  angle  bar. 

The  True  Form  of  the  Moulded  Edge.— Referring  to  Fig.  59 
place  the  moulded  edge,  A  B,  of  the  harpin  in  the  Body,  and  show  in 
the  half  siding  of  the  stem  C  D,  and  level  its  intersection  with  the 


70  NAVAL  ARCHITECTURE. 

harpin  at  E  into  the  Sheer,  cutting  inside  of  the  stem  at  E1.  Square 
this  point  down  into  the  Half  Breadth,  E-.  Lay  a  batten  on  A  B,  and 
lift  from  the  centre  line  at  A  the  distances  A  E,  A  H,  A  K,  A  B,  and 
place  these  in  the  Half  Breadth,  A  E  on  E-  E1,  and  the  others  on  their 
respective  stations  1,  2,  and  3.  Draw  a  curve  through  the  spots  which 
gives  the  expanded  moulded  edge.  A  pine  mould  is  made  of  this  line 
having  marked  on  it  the  position  of  the  frames  and  stem  termination, 
for  the  use  of  the  platform  men  in  bending  the  bar  to  its  true  form. 
The  height  above  the  base  on  the  stem  is  also  figured  upon  it. 

The  Form  of  the  Bevelled  Edge. — Set  down  below  the  moulded 
edge  in  the  Body  on  the  run  of  the  frames  the  depth  of  the  vertical 
flange  of  the  harpin  bar  E  e,  H//,  Kk,  Bb.  Pass  a  curve  through 
the  spots.  Draw  A  a  perpendicular  to  A  B,  and  level  over  the  point  e 
into  the  Sheer,  e1,  on  the  inside  of  the  stem,  and  drop  a  perpendicular 
from  the  point  on  to  the  Half  Breadth  centre.  Lay  a  batten  on  a  />, 
and  lift  from  a  the  distances  e,  //,  Z",  and  h,  and  set  them  out  from  the 
centre  Half  Breadth  line,  a  e  on  e2  e1  and  the  other  distances  on  their 
respective  stations.  Dot  the  line  in,  for  distinction,  which  gives  the 
form  of  the  bevelled  edge.  The  difference  between  this  and  the 
moulded  line  taken  at  any  point  square  to  the  moulded  edge  is  the 
bevel  required  for  the  vertical  flange,  the  flange  standing  out  from 
the  ship's  side  being  level  (see  Fig.  6o). 

The  Bevelling  Board. — Fig.  62.  A  piece  of  board  the  width 
of  the  vertical  flange  is  supplied  with  the  mould  showing  the  bevels 
at  each  frame  and  at  the  stem  point.  If  the  bevelled  edge  is  inside 
of  the  moulded  edge  in  the  Half  Breadth,  then  the  bar  must  be  "  open 
bevel,"  if  outside  shut  or  "  closed  bevel."  The  bevel  is  lifted  from 
the  board  and  applied  to  the  heel  of  the  bar  by  a  small  adjustable 
set  square.  Holes  are  punched  in  the  vertical  flange  at  each  frame 
for  attachment.  Fig.  61  shows  the  manner  of  applying  the  bevels, 
which  are  lifted  from  the  bevel  board  the  reverse  way  to  that  of 
marking  them  on  it.  The  amount  of  bevel  applied  to  the  bar  being 
the  distance  P  pins  a  right  angle,  except  when  less  than  a  right  angle. 

The  Sheer  Harpin,  which  is  also  made  of  angle  bar,  may  be  fitted 
at  the  fore  end  of  the  vessel,  being  made  parallel  to  the  ordinary  deck 
line.  Draw  in  the  Body  the  moulded  and  bevelled  edges,  and  project 
them  into  the  Sheer  and  Half  Breadth  plans.  In  Fig.  63,  A  E  is  the 
moulded  edge  in  the  Sheer.  The  moulded  edge  is  shown  a  deep  black 
line,  and  the  1  levelled  edge  a  fine  line. 


O 


o 

co 
X 

UJ 


RIBBANDS  AND  HARPINS.  71 

The  True  Form  of  the  Moulded  Edge. — Square  down  on  to  the 
Half  Breadth  centre  line  the  point  E,  where  the  harpin  cuts  the  inside 
of  the  stem.  Set  on  E1  E  the  half  siding  of  the  stem  at  E,  which 
gives  the  terminating  point.  Next  girth  from  the  point  E,  in  the 
Sheer,  the  positions  of  D,  C,  B,  and  A.  Lay  these  distances  off  from 
number  4  frame  along  the  centre  line  of  the  Half  Breadth,  and  draw 
up  perpendiculars  31,  21,  l1,  and  produce  level  lines  from  B1,  C1, 
D1,  E1,  the  cutting  points  of  the  original  frames  with  the  harpin  in 
its  true  position,  until  they  meet  the  new  perpendiculars,  which  are 
the  true  positions  of  the  frames  in  the  expanded  form.  A  curve 
passed  through  these  intersections  is  the  expanded  moulded  edge. 
A  yellow  pine  mould  is  made  to  this  line,  and  the  expanded  position, 
number  of  the  frames  and  ship  marked  upon  it. 

The  Bevelled  Edge. — Square  down  into  the  Half  Breadth  the 
point  e,  and  on  el  e  set  off  from  the  centre  the  half  siding  of  the  stem 
at  e,  which  gives  the  terminating  point.  Lay  a  batten  along  the 
bevelled  edge  in  the  Sheer  and  mark  on  it  the  positions  of  a,  b,  c,  d,  e. 
Place  the  batten  along  the  centre  of  the  Half  Breadth,  keeping  point 
a  fair  with  4  frame,  and  mark  corrected  position  of  the  frames. 
Draw  up  perpendiculars  from  these  points  to  cut  level  lines  produced 
from  the  intersection  of  the  frames  with  the  bevelled  edge  in  its  true 
position.  A  curve  through  the  spots  will  give  the  expanded  bevelled 
edge,  and  the  difference  between  this  line  and  the  moulded  edge  at  any 
point,  taken  square  to  the  latter  is  the  amount  of  bevel  placed  on  the  bar. 

The  Bevelling  Board. — Fig.  64.  A  piece  of  pine  . 
the  width  of  the  vertical  flange  of  the  harpin,  having 
on  the  bevels  taken  at  each  frame  is  supplied  with  the 
mould.  Holes  are  required  to  be  punched  in  the  vertical 
flange  for  temporary  attachment  to  the  frames.  The 
position  of  the  harpin  is  also  marked  on  the  frames 
and  stem  when  they  are  turned  ;  so  that  there  is  no 
difficulty  in  placing  the  harpin  in  its  right  position  on 
the  ship. 

Expansion  of  the  Moulded  Edge  in  the  Sheer. — Girth  the 
position  of  D,  C,  B,  and  A  from  E  on  the  Sheer  line  E  A,  and  set  them 
along  level  line  E  W  from  E.  Produce  perpendiculars  from  the  points, 
which  give  expanded  position  of  the  frames  1,  2,  3,  and  4,  on  which 
set  the  level  distances  of  the  frames  and  half  siding  of  the  stem  lifted 
from  the  Body.  A  line  run  through  the  spots  gives  expanded  moulded 
edge. 


y-       __   run 


or  the 


^IVEBSI^ 


OF 


RIBBANDS  AND  HARPINS.  71 

The  True  Form  of  the  Moulded  Edge.— Square  down  on  to  the 
Half  Breadth  centre  line  the  point  E,  where  the  harpin  cuts  the  inside 
of  the  stem.  Set  on  E1  E  the  half  siding  of  the  stem  at  E,  which 
gives  the  terminating  point.  Next  girth  from  the  point  E,  in  the 
Sheer,  the  positions  of  D,  C,  B,  and  A.  Lay  these  distances  off  from 
number  4  frame  along  the  centre  line  of  the  Half  Breadth,  and  draw 
up  perpendiculars  31,  21,  l1,  and  produce  level  lines  from  B1,  C1, 
D1,  E1,  the  cutting  points  of  the  original  frames  with  the  harpin  in 
its  true  position,  until  they  meet  the  new  perpendiculars,  which  are 
the  true  positions  of  the  frames  in  the  expanded  form.  A  curve 
passed  through  these  intersections  is  the  expanded  moulded  edge. 
A  yellow  pine  mould  is  made  to  this  line,  and  the  expanded  position, 
number  of  the  frames  and  ship  marked  upon  it. 

The  Bevelled  Edge. — Square  down  into  the  Half  Breadth  the 
point  e,  and  on  e1  e  set  off  from  the  centre  the  half  siding  of  the  stem 
at  e,  which  gives  the  terminating  point.  Lay  a  batten  along  the 
bevelled  edge  in  the  Sheer  and  mark  on  it  the  positions  of  a,  b,  c,  d,  e. 
Place  the  batten  along  the  centre  of  the  Half  Breadth,  keeping  point 
a  fair  with  4  frame,  and  mark  corrected  position  of  the  frames. 
Draw  up  perpendiculars  from  these  points  to  cut  level  lines  produced 
from  the  intersection  of  the  frames  with  the  bevelled  edge  in  its  true 
position.  A  curve  through  the  spots  will  give  the  expanded  bevelled 
edge,  and  the  difference  between  this  line  and  the  moulded  edge  at  any 
point,  taken  square  to  the  latter  is  the  amount  of  bevel  placed  on  the  bar. 

The  Bevelling  Board. — Fig.  64.  A  piece  of  pine 
the  width  of  the  vertical  flange  of  the  harpin,  having 
on  the  bevels  taken  at  each  frame  is  supplied  with  the 
mould.  Holes  are  required  to  be  punched  in  the  vertical 
flange  for  temporary  attachment  to  the  frames.  The 
position  of  the  harpin  is  also  marked  on  the  frames 
and  stem  when  they  are  turned  :  so  that  there  is  no 
difficulty  in  placing  the  harpin  in  its  right  position  on 
the  ship. 

Expansion  of  the  Moulded  Edge  in  the  Sheer. — Girth  the 
position  of  D,  C,  B,  and  A  from  E  on  the  Sheer  line  E  A,  and  set  them 
along  level  line  E  W  from  E.  Produce  perpendiculars  from  the  points, 
which  give  expanded  position  of  the  frames  1,  2,  3,  and  4,  on  which 
set  the  level  distances  of  the  frames  and  half  siding  of  the  stem  lifted 
from  the  Body.  A  line  run  through  the  spots  gives  expanded  moulded 
edge. 


72  NAVAL  ARCHITECTURE. 

The  Stern  Harpin  is  also  made  of  angle  bar,  and  appears  a  level 
line  in  the  Body  and  Sheer  plans.  It  is  placed  in  between  the  rail  and 
knuckle  for  securing  the  stern  cants  in  position,  until  the  after-deck 
stringer  or  bulwark  plates  are  in  place.  Its  extent  is  from  two  frames 
on  one  side  to  two  on  the  other. 

The  Moulded  Edge. — In  Fig.  65  the  line  AB  and  ab  is  the 
moulded  edge  in  the  Sheer  and  Body.  Square  down  into  the  Half 
Breadth  from  the  Sheer  the  intersection  of  the  moulded  edge  with  the 
buttocks  and  centre  line,  and  lift  from  the  Body  the  distances  c,  d,  b 
from  a,  and  set  them  off  in  the  Half  Breadth  on  their  respective 
frames.  Draw  line  in,  which  will  be  moulded  edge  of  the  harpin  in 
its  true  form,  which  is  also  the  expanded  form. 

The  Bevelled  Edge. — Set  off  in  the  Sheer  from  A  on  the  run  of 
the  stern  and  the  buttocks  and  the  frames  in  the  Body  the  depth  of 
the  harpin  bar,  and  square  the  points  down  from  the  Sheer  into  the 
Half  Breadth.  Lift  the  distances  of  the  frames  T,  1  and  2,  from  the 
centre  of  the  Body  on  the  bevelled  edge  and  set  them  off  in  the  Half 
Breadth  on  their  respective  frames.  A  curve  drawn  through  the 
points  will  give  the  form  of  the  bevelled  edge.  Show  in  the  moulded 
edge  of  the  cants  in  the  Half  Breadth  :  then  the  difference  between  the 
moulded  and  bevelled  edges  square  to  the  first  is  the  bevel  on  the 
vertical  flange.  A  yellow  pine  mould  is  made  to  the  moulded  edge 
showing  the  positions  of  the  centre  line,  cants,  and  frames  T,  1  and  2. 
Bevels  are  lifted  at  centre,  cants,  and  square  frames,  and  placed  on  a 
piece  of  board  the  width  of  the  vertical  flange.  Holes  are  punched  by 
the  frame-turners  in  the  vertical  flange  of  the  bar  for  attaching  the 
harpin  to  the  cants  and  frames.  The  mould  may  be  reversed  on  the 
boards  for  getting  the  shape  of  the  opposite  side  of  the  ship.  This 
harpin  is  not  used  in  all  yards. 


Note. — These  harpin  bars  do  not  of  necessity  require  bevelling,  except  in 
extreme  cases.  Of  course,  where  the  cants  do  not  extend  so  high,  it  should  be 
placed  lower  down. 


74  NAVAL  ARCHITECTURE. 


CHAPTER  VIII. 

Principal  Moulds,  and  the  order  they  are  sent  into  the  Yard — Stem— Stern 
Frame — Shaft  Struts — Stern  Tubes— Flat  Plate  Keel— Centre  through 
Plate  Keelson — Boat  Beams. 


MOULDS. 

Wood  moulds,  or  templates,  are  made  in  the  loft  of  various  parts 
of  the  vessel  for  the  use  of  the  platers  and  others,  for  forming  the 
material  into  its  proper  shape.  The  principal  of  these,  and  the 
order  in  which  they  should  be  sent  out,  is  as  follows  :  — 

1.  Flat  keel  plate. 

2.  Centre  keelson  plate,  with  templates  for  vertical  bars. 

3.  Beam  camber,  with  templates  for  knees. 

4.  Stem  and  stern  post  club-foot  sections. 

5.  Struts  and  stern  tubes  in  twin  screws. 

6.  Stern  cants. 

7.  Stem. 

8.  Stern,  common,  and  sheer  harpins. 

9.  Stern  expansion  and  set  moulds. 

10.  Stringer  plates. 

1 1 .  Cargo  hatches. 

12.  Deck-houses. 

13.  Clipper  stem  lacing  piece,  bowsprit,  trail  board,  and  figure  block. 

14.  Boat  beams. 

15.  Hawse-pipes. 

Nos.  1,  2,  4,  5,  7,  and  14,  are  described  in  this  chapter ;  and  Nos. 
3,  6,  8,  9,  10  to  13  and  15,  on  pages  34,  32,  G9,  50,  88  and  96, 
respectively. 

The  Stem. — In  mercantile  vessels  it  is  made  of  solid  iron,  of 
rectangular  section.  Where  a  flat  plate  keel  is  associated,  the  foot 
usually  has  a  club,  as  shown  in  Fig.  66,  with  a  recess  on  the  lower 
edge  for  the  scarph  of  the  keel.  When  the  ship  is  faired-up  on  the 
loft  floor,  section  moulds  are  given  to  the  forge  to  form  the  foot.  A 
flat  mould  of  pine  (shown  by  Fig.  G7)  is  made,  in  the  meantime,  to  the 
inside  edge  of  the  stem  for  turning  the  bar  to  its  shape  on  the  yard 
bending  slabs.  This  mould  has  marked  on  it  the  position  of  the  keel 
scarph  (approximately),  frames,  shell  plate  landing  edges,  ribbands, 
decks,  and  a  level  or  water-line  on,  or  about,  the  load  draft.     Before 


MOULDS. 


75 


turning  the  bar,  the  position  of  the  plate  or  bar  keel  ending  on  the 
building  blocks,  should  be  lifted  relative  to  an  adjacent  frame,  and 
transferred  on  to  the  mould.  It  will  be  readily  seen  that,  to  secure 
the  designed  length,  this  should  be  carefully  done ;  besides,  any 
mistake  would  affect  the  end  shell-plates.  Where  the  stem,  above  the 
forefoot,  is  not  square  to  the  keel  base,  a  perpendicular  is  lined  on  the 
mould  and  transferred  to  the  stem  after  turning,  beside  the  position 

Fig.  66. 


SHEER 


of  the  shell-plate  edges,  decks,  and  ribbands.  The  height  of  the 
level  line  is  centre-punched  on  the  fore  edge  of  the  bar ;  which  will 
be  found  useful  in  erecting.  In  some  yards  the  rivet  holes  are  drilled 
in  the  bar  previous  to  turning,  leaving  out  those  in  way  of  the 
landing  edges  until  the  ship  is  faired-up  on  the  blocks.  The  better 
plan  is  considered,  where  convenient,  to  drill  these  holes  after  the 
bar  is  in  form. 

In  soaie  cases,  instead  of  the  club-foot,  an  angle  bar,  or  flanged 
plate,  is  tapped  on  to  the  stem  bar  to  take  the  keel  and  garboard  strakes. 
This  is  shown  in  Fig.  68. 


Fig.   67 


rw<TWP 


SCARPH 


MOULDS. 


77 


The  form  of  the  stem  scarph,  when  associated  with  "side  bar 
keel,"  is  given  in  Fig.  69. 

Stern  Frame. — The  forge  usually  makes  its  own  moulds  from 
a  complete  figured  drawing  on  a  scale  of  half  an  inch  to  a  foot,  which 
is  supplied  by  the  shipbuilder,  together  with  enlarged  detail  figured 
sketches  of  riveting,  gudgeons,  boss,  etc.     In  the  case  of  a  flat  keel  a 

Fig.   68. 


I40  &  141 


14-2 


club-foot  is  fitted  in  most  yards,  and  for  the  purpose  of  forming  this, 
after  the  ship  is  faired-up  on  the  loft  floor,  section  moulds  are  supplied 
to  the  forge. 

Shaft  Struts  or  After  Brackets  in  Twin  Screws. — They  are 
usually  made   of  cast  steel.     For  the  purpose  of  accuracy  it  is  the 


78 


NAVAL  ARCHITECTURE. 


custom  for  the  loftsman  to  make  a  template  or  drawing,  Fig.  70, 
from  the  loft  floor  lines,  through  the  athwartship  centre,  showing  the 


Fig.  69. 

ELEVATION 


-rr 


■  SCARPA 


-Ui 


SCARPH 


PLAN 


spread  of  the  legs,  boss,  and  rough  bore.      This  is  tried  upon  the 
ship  when  in  frame,  before  it  is  sent  to  the  works,  from  which, 

in  conjunction  with  a 


Fig.   70. 


STRUTS   OR 
STERN   BRACKETS 


inexpensive  method  is  shown  on  page   13. 


figured  drawing  or  trac- 
ing, moulds  for  casting 
are  made.  It  may  be 
necessary  to  give  bevels 
for  shafts.  Where  the 
palms  are  planted  on 
the  outside  of  the  shell 
plating,  sectional  tem- 
plates of  the  ship's  side 
should  be  supplied  to 
form  patterns.  A  tem- 
plate of  T  form  is 
generally  made,  show- 
ing the  character  of  the 
shell. 

Stern  Tubes  in 
Twin  Screws. — 
There  are  many  ways 
of  finishing  off  the 
apertures  for  the  shafts 
in  the  sides  of  a  ves- 
sel. A  simple  and 
In   that   case   a   cast 


steel  hollow  ring,  reproduced    on    a    larger    scale   in    Fig.    71,    is 


MOULDS. 


79 


attached  to  the  framing  D.  The  shell  plating  B  and  B1  is  lapped 
round  the  fore  and  aft  rim  A,  and  connected  with  a  substantial 
number  of  rivets.  On  the  after  side  of  the  ring  there  is  a  projecting 
flange  C  and  C1,  with  a  rabbet  to  take  shell  plating.  To  cast  these 
rings,  a  full  sized  section  is  laid  down  on  a  board  (see  E  F),  and 
a  view  of  the  after  and  forward  sides  of  the  ring  drawn  alongside. 
This  is  sent  to  the  works,  who  make  their  own  moulds.  In  vessels  of 
larger  power  this  ring  may  be  lengthened  (see  Fig.  72),  and  additional 
projecting  pieces  a  and  h  made  for  taking  partial  bulkheads.  The 
shell  plating  laps  on  to  the  ring  at  d  and  d1,  and  the  sides  have  a  web 
c  and  c1  to  take  the  plating.  For  making  moulds,  for  casting,  a  full 
sized  drawing  on  a  board  is  sent  to  the  works  showing  longitudinal 

Fig.  71. 

STERN    TUBE    RINQ 


WIEW  LOOKING  AFT 


and  cross  sections.  Skeleton  moulds  would  be  better  tried  on  the 
ship  before  being  sent  away. 

Sometimes  these  rings  are  forged. 

Flat  Plate  Keel. — Two  small  scrieve  boards,  about  3  feet  square, 
are  supplied  to  the  yard,  showing  the  form  of  the  bottom  at  each 
frame  for  the  extent  of  the  keel.  Those  which  are  shown  in  Figs.  73 
and  74  are  given  in  conjunction  with  the  wood  template,  Fig.  75, 
having  longitudinal  pieces  A  and  A1  the  width  of  the  seams,  the 
outside  edges  representing  the  expanded  breadth  of  the  plate,  with 
pieces  nailed  across  showing  the  shell  flange  of  the  frames.  The 
heavy  line  in  the  sketch  being  the  heel  of  the  bar,  which  is  planed  to 


80 


NAVAL  ARCHITECTURE. 


distinguish  it.  End  pieces  D,  nailed  on,  show  the  position  and  width 
of  the  laps,  or  half  the  butt  strap  when  flush.  Care  should  be  taken 
to  get  the  sides  of  the  template  perfectly  parallel,  and  the  ends  square, 
to  the  centre.  Then  the  centre  lines  for  the  edge  holes  and  centre 
bars  may  be  struck  in  the  full  length,  and  on  the  crosspieces  for  the 
frames.  A  piece  of  board  is  now  got  perfectly  rectangular,  the  width 
of  the  plate  and  the  length  of  the  butt  lap,  upon  which  is  divided  off 

Fig.    72, 


VIEW  AT  AFT -N  END, 


'S&VIEW  AT  FORE  END 


the  rivet  holes,  as  shown  in  Fig-.  75,  to  take  seams  and  centre  bars. 
This  is  placed  fair  upon  one  end  of  the  template  and  tacked  in  position, 
and  the  holes  bored  through  it  and  the  template  at  the  same  time. 
It  is  then  taken  off  and  holes  marked  off  from  it  on  the  other  end  of 
the  template,  after  which  the  longitudinal  seam  and  the  frame  holes 
are  divided  in  and  bored  out.  It  will  be  noticed  that  only  one  hole  is 
placed  through  each  seam  in  way  of  the  frames,  which  is  next  to  the 
outside  sight  edges  of  the  keel  plate  for  caulking  purposes.     All  the 


MOULDS. 


81 


keel  plates  may  be  marked  off  from  this  template,  while  the  set  on 
the  plates  is  lifted  from  the  scrieve  boards,  Figs.  73  and  74. 

A  batten  template  of  the  holes  should  be  given  to  the  frame 
turner  in  order  that  those  in  the  frames  may  be  made  to  agree. 


Fig. 
AFTER 


73. 
BODY. 


Fig.  74. 
FORE    BODY. 


In  some  cases  it  is  best  to  lift  the  set  of  the  foremost  and  after- 
most plates  from  the  ship,  especially  that  part  in  way  of  the  club-foot 
of  the  stem  and  stern  posts. 

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MOULDS. 


88 


Fig.  76. 

SECTION 

F7 


KEELSON 


Centre  through  Plate  Keelson. — The  plates  are  more  easily 
worked  when  of  uniform  length.  Two  duplicate  wood  templates  are 
made  for  marking  off  in  the  case  of  a  flat  plate  keel,  and  one  with  a 
side  bar  keel. 

Fig.  76  shows  such  a  template,  the  lines  for  which  are  marked  off 
on  the  loft  floor.  The  top  edge  is  parallel  to  the  bottom,  the 
longitudinal  pieces  A  and  A1  being  the  width  of  the  vertical  flanges 
of  the  top  and  bottom  bars  respectively,  to  which  pieces  B,  B1 
are  nailed,  showing  the  position  and  width  of  the  vertical  bars, 
with  the  edges,  representing  the  heel,  planed.  Pieces  C  show  the 
position  and  width  of  the  butts.  The  holes  in  the  longitudinal  bottom 
bars  are  slightly  reeled.  A  piece 
of  board,  perfectly  rectangular,  is 
made  the  width  of  the  plate  and 
the  length  of  the  butt,  upon  which 
the  rivet  holes  are  arranged  to  take 
the  top  and  bottom  bars ;  this  is 
tacked  into  position  on  the  end  of 
the  template,  and  the  holes  bored 
through  both.  It  is  then  lifted 
and  transferred  i-o  the  other  end, 
and  the  holes  marked  off  and  bored. 
The  top  and  bottom  and  vertical 

bar  holes  may  now  be  divided  into  KEEL 

the  regulation  spacing  and  bored. 

A  duplicate  template  may  be  marked  off  by  laying  one  on  top  of 
the  other,  or  tacking  temporarily  two  templates  together  in  the  first 
case,  and  boring  holes  through  at  the  same  time. 

A  separate  strip  template  is  given  to  the  apprentice  platers,  show- 
ing the  length  of  and  holes  in  the  vertical  bars  B,  B1,  and  another 
template  showing  those  in  the  other  flange  attached  to  the  floor.  A 
copy  of  the  latter  is  also  given  to  the  board-men,  to  punch  floors  to 
receive  vertical  bars. 

In  the  case  of  a  centre  through  plate  keelson  with  a  side  bar  keel, 
the  template  is  only  made  to  the  top  of  the  side  slabs,  the  plate  being 
punched  above  the  keel  first  and  afterwards  attached  to  side  slabs,  and 
the  three  thicknesses  drilled  through.  The  holes  in  the  keel  are  set  off 
by  the  loftsman  to  the  regulation  distance.  It  is  best  to  make  a  short 
template  the  width  of  the  keel,  with  the  holes  bored  through,  that  can 
be  shifted  as  each  plate  is  drilled. 


84 


NAVAL  AECHITECTURE. 


Boat  Beams. — Draw  in  on  the  loft  floor  the  form  of  the  ship's 
side  in  way  of  each  beam.  In  Fig-.  77  fix  the  height  A  at  the  centre 
line,  such  that  yon  have  comfortable  head  room  at  the  sides  below  the 
web  of  the  beam.  Draw  in  camber  line  A  B  and  connect  it  at  E 
with  side,  C  D  produced.  A  skeleton  wood  mould  is  made  to  the  line 
C  D  B  A,  showing  the  correct  length  and  the  centre.  Cross  battens 
to  keep  it  in  form  are  fitted  from  D  to  A,  and  from  DA  to  E  B  A 
edge.  It  may  be  found  necessary  where  there  is  ^considerable  difference 
of  the  vessel's  side  to  make  several  moulds.     Sometimes  these  beams 


Fig.   77. 

BOAT   BEAMS 


only  extend  to  the  deck  erections,  in  other  cases  they  are  butted  at 
the  centre,  or  a  little  to  the  sides.  In  any  case  a  half  mould  ought  to 
answer  the  purpose,  if  the  centre  is  correctly  marked  for  each  beam. 


POOP  ROUND  AND  TURTLE  BACK.  85 


CHAPTER  IX. 

Pooj)  Round :  Obtaining  Lines  and  Fairing-up— Expansion  of  Plating.     Turtle 
Back :  How  to  Obtain  and  Fair-up  the  Form,  Expansion— Plate  Edges. 


POOP  BOUND  AND  TURTLE  BACK. 

The  majority  of  sailing  ships  and  steamers  are  fitted,  above  the 
upper  deck,  with  after  and  forward  short  erections  for  the  berthing  of 
the  crew,  and  for  protection  from  seas.  That  aft  is  called  a  poop,  and 
forward  a  forecastle.  To  prevent  these  erections  from  giving  a  heavy 
appearance  to  the  vessel,  they  are  usually  rounded  away  at  the  sides 
above  the  main  rail.  In  many  cases,  especially  in  West  of  England 
built  vessels,  the  forecastle  assumes  a  turtle  back  form.  The  method 
of  deciding  and  working  out  the  form,  and  other  points,  of  these  will 
now  be  described. 

To  Obtain  the  Lines  and  Fair = up  a  Poop  Round. — In 
Fig.  78,  draw  in  the  Sheer  the  poop  deck  at  the  centre  line  A  B  ; 
and  through  the  point  C,  the  top  of  the  rail,  describe  the  quadrant 
of  a  circle  to  meet  the  line  A  B  at  B.  This  line  C  B  A  is  the  form 
of  the  poop  at  the  centre  line.  Set  up  level  lines  a  b  and  c  d,  about  9 
inches  apart,  above  the  rail  height  C  to  cut  the  round.  Square 
down  on  to  the  Half  Breadth  centre  line  the  intersection  of  these  level 
lines  with  the  circular  part  C  B,  and  the  position  of  B  or  poop  angle  bar. 
Run  lines  ef,  g  h,  and  B1  E,  from  these  points,  parallel  to  the  rail. 
Then  square  up  on  to  the  rail  in  the  Sheer  the  position  of  the  buttocks, 
and  set  9  and  18  inch  sheer  lines  above  these  points.  Project  up 
from  the  Half  Breadth  on  to  their  respective  sheer  lines  the  inter- 
section of  the  buttocks  and  points  on  B1  E.  Place  the  sheer  lines  in 
the  Body  above  the  T,  1,  2,  and  3  section  rail  heights.  Lift  from  the 
Half  Breadth  the  positions  of  ef,  y  h,  and  B1  E  on  the  T,  1,  2,  and  3, 
and  lay  them  off  on  corresponding  sheer  lines  at  each  body  section 
square  out  from  the  centre.  Next  mark  off,  on  the  centre  line  of  the 
body,  the  deck  centre  heights  on  the  T,  1,  2,  and  3,  and  draw  in 
curve  of  the  beam  in  each  case  from  camber  curve  given  in  the  figure  ; 
and  connect  the  curve  with  the  corresponding  spots  on  the  sheer 
lines,  set  off  for  the  round,  maintaining  the  height  of  B  above  C  01 
at  the  angle  bar.  This  will  give  you  the  form  of  the  poop  on  T,  1,  2, 
and  3,  which  may  be  checked  by  transferring  the  heights  above  the 
level  line  on  each  buttock  into  the  Sheer,  and  connecting  them  by  fair 


86  NAVAL  ARCHITECTURE. 

curves  with  the  spots  on  the  round,  already  projected  from  the  Half 
Breadth.  If  these  lines  are  faired  in  each  plan,  as  you  proceed,  it  will 
be  found  that  sections  taken  square  to  the  rail  in  the  Half  Breadth 
are  circular,  corresponding  with  the  centre  line  C  B.  Cant  No.  4  is 
shown  projected  into  the  Sheer  :  the  height  on  T  may  be  found  by 
setting  off  T  D  in  the  Body  on  the  transom  camber  curve,  and  lifting 
the  point,  D1  E,  from  the  level  line  into  the  Sheer  T  D2.  The  forma- 
tion of  a  poop  side  of  a  natter  form  is  found  in  the  same  way,  after 
the  centre  C  B  is  settled. 

Expansion  of  a  Poop  Round. — In  Fig.  79  show  the  cants  in 
position  in  the  Half  Breadth,  and  arrange  the  butts  of  the  plating  to 
clear.  Girth  the  rail  in  the  Half  Breadth  for  the  position  of  the 
moulded  edge  of  the  cants,  square  frames  T  and  1.  Set  these  off 
along  the  expansion  level  line,  and  erect  perpendiculars  from  the  points, 
on  which  lay  off  respective  sheer  heights,  lifted  from  the  Sheer  above 
the  level  line  — that  is,  the  centre,  cants,  frames  T  and  1,  and  draw  a 
curve  through  the  spots.  This  is  the  bottom  edge  of  the  rail  line 
expanded :  the  top  edge  of  the  rail  may  be  drawn  parallel  to  it,  the 
depth  of  the  moulding.  Girth  the  centre  line  section  in  the  Sheer, 
from  the  top  of  the  rail,  for  the  position  of  a,  h,  c,  and  d,  and  put  these 
distances  out  on  the  centre  line  in  the  expansion  A1,  a\  hl,  c1,  and  d\ 
and  line  in  curves  a\  b\  c\  etc.,  through  the  spots  parallel  to  the  rail. 
In  the  plan  show  in  lines  <?/,  gh,  Id,  mn,  op,  square  to  the  rail  and  about 
the  centre  of  each  plate.  Then  girth  the  rail  for  their  position,  and 
transfer  them  into  the  expansion  along  the  rail  A1  A2,  and  from  the 
points  erect  perpendiculars  to  the  rail  curve  :  the  correction  for  the 
slight  sheer  of  rail  can  be  made  if  considered  desirable.  Girth  in  the 
Half  Breadth  the  width  of  each  plate  to  its  butt  on  each  side  of  these 
centre  lines,  along  the  rail,  sheer  lines,  angle  bar,  and  inner  edge,  and 
set  them  off  in  the  expansion  on  each  side  of  the  centre  lines  exf\  tj{  //', 
etc.,  tracing  curves  through  the  spots  as  shown  by  heavy  lines,  which 
will  give  the  true  form  of  the  plate  in  each  case.  In  ordering,  allow 
for  "  sny,"  also  round  and  hollow  at  the  ends  Care  must  be  taken, 
when  fixing  the  point  d,  that  the  plate  is  sufficiently  wide  to  take  the 
margin  plank  and  deck  ends. 

Turtle  Back.  — In  Fig.  80,  draw  down  the  form  of  the  rail  in  the 
Sheer,  Half  Breadth,  and  Body,  for  the  extent  of  the  turtle  back ;  and 
line  in  the  position  and  form  of  the  buttocks  in  each  plan  from  level 
line  to  the  rail,  also  the  frames  T,  1,  2,  and  3  ;  putting  in  A,  B,  C,  and 
I)  temporary  sections  abaft  of  the  transom:  then  you  are  ready. 


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POOP  ROUND  AND  TURTLE  BACK.  87 

To  Obtain  Lines  for  the  Turtle  Back. — Settle  the  height,  E, 
from  the  upper  deck,  and  the  form  of  the  line,  E  A,  at  the  centre  of 
the  ship  ;  lift  the  heights  on  each  section  above  the  level  line,  and 
transfer  them  on  to  the  centre  in  the  Body  above  the  corresponding 
level  line.  Draw  in  the  Body  the  required  form  of  the  cross  section 
on  3  frame,  usually  a  fuller  line  than  the  ordinary  camber  curve 
explained  on  page  33,  also  the  transom  cross  section,  about  the  same 
curve  as  No.  3  frame.  Transfer  into  the  Sheer,  from  the  Body  above 
the  level  line,  the  cutting  points  of  3  and  T  on  alternate  buttocks, 
and  run  fair  line  to  the  terminations  on  the  rail ;  somewhat  like  the 
centre,  only  gradually  spread  towards  the  after  end.  Make  any  correc- 
tion you  find  necessary  for  fairness  in  the  Body  and  Sheer  before  run- 
ning the  other  buttocks ;  then  the  intermediate  cross  sections  can  be 
readily  drawn  in  by  lifting  the  sheer  heights  on  the  buttocks  and 
transferring  them  into  the  Body. 

Sheered  lines  may  be  used  for  obtaining  and  fairing  form  in  con- 
junction with  the  buttocks.  They  are  first  placed,  as  shown  in  the 
Sheer,  about  6  inches  and  12  inches  parallel  to  the  rail ;  their  inter- 
section with  the  buttocks  are  squared  down  into  the  Half  Breadth. 
More  points  may  be  got  by  placing  the  sheered  lines  in  the  Body,  and 
transferring  widths  on  the  frame  stations  into  the  Half  Breadth. 
These  lines  would  enable  you  to  place  an  additional  check  upon  the 
previous  fairness. 

The  cants  are  shown  in  the  Sheer  dotted,  projected  from  the  Half 
Breadth  in  conjunction  with  the  heights  on  the  transom  lifted  from 
the  Body. 

To  Expand  the  Form  of  a  Turtle  Back. — It  is  considered 
sufficiently  accurate  to  girth  the  centre  line  E  A  in  the  Sheer  for  the 
position  of  the  frames,  and  the  point  A  from  E ;  and  set  them  off 
from  3  on  the  centre  line  of  the  Half  Breadth,  from  which  points  erect 
perpendiculars,  and  on  them  lay  off  the  girthed  widths  of  the  cross 
sections.  It  is  necessary  to  girth  the  front  section  No.  3  for  the 
position  of  the  buttocks,  and  place  them  in  the  Half  Breadth  parallel 
lines  to  the  centre,  on  which  are  plotted  off  the  girthed  lengths  of  the 
sheer  buttocks  from  3  frame.  This  will  give  you  sufficient  spots  to 
draw  in  the  curve  of  the  expanded  form  of  half  of  the  turtle  back  P  K. 
Allowance  should  be  made  at  the  outside  edges  for  connection  to  other 
plating,  usually  3  inches  round  the  sides  and  the  width  of  the  beam 
flange  at  the  fore  end.  The  plate  edges  are  made  parallel  to  the 
centre  line,  and  the  cants  and  butts  arranged,  after  which  the  plates 
may  be  measured  off'  and  ordered. 


Of  CALlS*)^ 


DOOP  ROUND  AND  TURTLE  BACK.  87 

To  Obtain  Lines  for  the  Turtle  Back.— Settle  the  height,  E, 
from  the  upper  deck,  and  the  form  of  the  line,  E  A,  at  the  centre  of 
the  ship  ;  lift  the  heights  on  each  section  above  the  level  line,  and 
transfer  them  on  to  the  centre  in  the  Body  above  the  corresponding 
level  line.  Draw  in  the  Body  the  required  form  of  the  cross  section 
on  3  frame,  usually  a  fuller  line  than  the  ordinary  camber  curve 
explained  on  page  33,  also  the  transom  cross  section,  about  the  same 
curve  as  No.  3  frame.  Transfer  into  the  Sheer,  from  the  Body  above 
the  level  line,  the  cutting  points  of  3  and  T  on  alternate  buttocks, 
and  run  fair  line  to  the  terminations  on  the  rail ;  somewhat  like  the 
centre,  only  gradually  spread  towards  the  after  end.  Make  any  correc- 
tion you  find  necessary  for  fairness  in  the  Body  and  Sheer  before  run- 
ning the  other  buttocks  ;  then  the  intermediate  cross  sections  can  be 
readily  drawn  in  by  lifting  the  sheer  heights  on  the  buttocks  and 
transferring  them  into  the  Body. 

Sheered  lines  may  be  used  for  obtaining  and  fairing  form  in  con- 
junction with  the  buttocks.  They  are  first  placed,  as  shown  in  the 
Sheer,  about  6  inches  and  12  inches  parallel  to  the  rail ;  their  inter- 
section with  the  buttocks  are  squared  down  into  the  Half  Breadth. 
More  points  may  be  got  by  placing  the  sheered  lines  in  the  Body,  and 
transferring  widths  on  the  frame  stations  into  the  Half  Breadth. 
These  lines  would  enable  you  to  place  an  additional  check  upon  the 
previous  fairness. 

The  cants  are  shown  in  the  Sheer  dotted,  projected  from  the  Half 
Breadth  in  conjunction  with  the  heights  on  the  transom  lifted  from 
the  Body. 

To  Expand  the  Form  of  a  Turtle  Back. — It  is  considered 
sufficiently  accurate  to  girth  the  centre  line  E  A  in  the  Sheer  for  the 
position  of  the  frames,  and  the  point  A  from  E  ;  and  set  them  off 
from  3  on  the  centre  line  of  the  Half  Breadth,  from  which  points  erect 
perpendiculars,  and  on  them  lay  off  the  girthed  widths  of  the  cross 
sections.  It  is  necessary  to  girth  the  front  section  No.  3  for  the 
position  of  the  buttocks,  and  place  them  in  the  Half  Breadth  parallel 
lines  to  the  centre,  on  which  are  plotted  off  the  girthed  lengths  of  the 
sheer  buttocks  from  3  frame.  This  will  give  you  sufficient  spots  to 
draw  in  the  curve  of  the  expanded  form  of  half  of  the  turtle  back  P  K. 
Allowance  should  be  made  at  the  outside  edges  for  connection  to  other 
plating,  usually  3  inches  round  the  sides  and  the  width  of  the  beam 
flange  at  the  fore  end.  The  plate  edges  are  made  parallel  to  the 
centre  line,  and  the  cants  and  butts  arranged,  after  which  the  plates 
may  be  measured  otf  and  ordered. 


88  NAVAL  ARCHITECTURE. 


CHAPTER|X. 

Expansion    of  a  Stringer  Plate  with  no  Sheer   and   with   Sheer— Template- 
Allowance  for  Knees  in  Ordering  Tee  Beams,  and  in  Bulb  Plates. 


EXPANSION  OF  A  STRINGER  PLATE  AND  BEAM  KNEES. 

Expansion  of  a  Stringer  Plate.— Sometimes  the  stringer  plate 
edges  are  expanded  on  the  loft  floor  for  the  purpose  of  making  wood 
templates  for  the  platers.  It  is  sufficient,  where  the  deck  at  the  side 
is  practically  level,  to  set  off  the  spacing  of  the  beams,  and  on  them 
from  the  side  curve  to  lay  off  the  widths  of  the  plate  :  but  when  the 
deck  has  considerable  sheer,  like  Fig.  8 1,  it  is  necessary  to  girth  the 
sheer  line  for  the  position  of  the  butts  and  beam  points  a,  b,  c,  d,  e,f, 
//,  h,  and  k,  and  lay  them  out  on  a  level  line  A  P>,  giving  points  a,  b\ 
c1,  d1,  etc.,  which  extend  square  to  the  centre  line  over  the  stringer. 
Produce  level  lines  through  the  intersection  of  the  outer  edge  of  the 
stringer  plate  with  the  original  beam  lines,  until  they  cut  the 
expanded  beam  lines  at  b'\  c2,  d2,  etc.,  which  intersection  gives  points 
for  the  expanded  edge  of  the  stringer,  shown  in  the  figure  by  a 
dotted  line.  From  this  edge  on  the  expanded  beams  set  off  the  width 
of  the  stringer  plate,  and  draw  inner  edge  through  the  spots  ;  and 
then  fix  the  butts.  The  figure  C  D  E  F  is  the  expansion,  for  which 
a  wood  skeleton  mould  is  made  showing  edges,  butts,  and  beams  in 
the  usual  way.  The  holes  for  the  beams  are  generally  lifted  from  the 
ship  by  applying  template  in  position,  and  marking  from  the  under- 
side on  the  crosspieces  with  a  circular  piece  of  wood  dipped  in  liquid 
whitening.  Those  for  the  edges  and  butts  are  divided  in  along  the 
side  battens.  The  holes  for  beams  may  be  marked  from  the  beam 
battens,  which  were  used  for  lining  off  the  holes  in  the  beams. 

To  Find  the  Allowance  for  Beam  Knees  or  Arms.— The 
Classification  Registry  rules  require  that  the  depth  of  beam  knees 
should  be  twice  and  a  half  the  depth  of  the  beam  web,  and  once  and 
a  half  the  depth  across  the  throat.  For  special  reasons  it  is  some- 
times more.  Knees  to  tee  beams  are  best  formed  by  sawing  up  the 
depth,  and  turning  the  lower  part  down  to  form  the  knee  :  a  piece  of 
plate  being  welded  into  the  angular  vacancy.  In  ordering,  when  done 
in  this  fashion,  allowance  for  turning  down  has  to  be  made  over  the 


90 


NAVAL  ARCHITECTURE. 


width  of  the  deck  plan.  In  Fig.  82  the  tee  beam  knee  is  shown  in 
position.  Girth  the  centre  line  a  b  of  the  turned  down  part,  and  set 
it  out  straight  c/1  &,  then  c  d  is  the  extra  allowance  for  one  side  of  the 
ship,  which  works  out  in  practice  about  the  depth  of  the  beam  over 
the  half  length. 

By  Fig.  83  it  will  be  seen  that,  at  the  ends  of  the  ship,  less  than 
the  midship  allowance  would  do  owing  to  the  fall  in  of  the  side.     The 


Fig.   82. 


T 


a — 


Fig.  83. 


T 


Fig.  84. 


Fig.  85. 


wisest  course  is  to  draw  a  line  in  conjunction  with  the  deck  plan, 
showing  the  allowance  at  each  beam.  This  line  may  be  easily  found 
by  trying  a  few  sections. 

Fig.  84  shows  a  bulb  plate  beam  which  is  turned  down  bodily,  and 
a  piece  welded  in  the  top  corner.  Draw  in  the  centre  line  a  b.  Girth 
this  line,  and  set  the  distance,  b  a1,  out  straight.  Then  c  d  is  the 
allowance  for  each  side.  The  end  allowance  may  be  reduced  (see 
Fig.  85). 


Note. — It  may  be  mentioned  that  the  difference  between  the  level  width 
of  a  deck  and  the  girthed  width,  allowing  for  the  ordinary  camber,  is  about  one 
inch  on  the  midship  beam. 


DIA.    A 


Fig.  86. 


IRON  AND  STEEL  MASTS.  91 


CHAPTER  XI. 

How  to  Obtain  the  Form  —Expansion  —Doubling  at  Deck — Doubling  at  Heel — 

Mast  Tube  Expansion. 


IEON  AND  STEEL  MASTS. 

Masts  are,  in  the  most  of  cases,  tapered  and  raked  aft,  the  rake 
varying  from  \  to  2|  inches. 

To  Obtain  the  Form. — The  diameter  at  the  head  is  about  five- 
eighths  and  the  heel  about  three-fourths  of  the  deck  diameter.  Draw 
down  in  Fig.  86  a  straight  line  the  length  of  the  lower  mast,  on  a 
scale  of  ^  inch  to  the  foot.  Let  this  line  A  B  be  the  centre,  and  on  it 
set  off  the  correct  positions  of  the  heel,  deck,  and  head.  The  housing 
is  best  measured  from  the  Sheer  Draught,  making  allowance  for 
camber  of  beam.  On  A  B,  produced  clear  of  the  heel,  describe  the 
circle  a  b  c,  with  diameter  equal  to  that  required  at  the  deck.  From 
the  points  a  and  c  describe  arcs  a  D  and  c  D  with  radii  a  c.  Find  a 
jDoint  ef,  between  the  arcs,  equal  to  the  decided  diameter  at  the 
head.  Divide  G  H  into  a  suitable  number  of  equal  spaces,  say  four, 
and  level  lines  through  the  points  to  the  arcs.  Divide  the  distance 
on  the  line  A  B,  between  deck  and  head,  into  the  same  number  of 
equal  spaces  as  G  H,  and  square  points  across  the  plan.  Lift  from 
the  section,  a  c,  op,  mn,gli,  and  ef,  around  G  H,  and  set  them  off 
on  their  corresponding  lines,  a1  c1,  o}p\  m1  n1,  cf  A1,  and  e1/1,  divided 
equally  on  each  side  of  the  centre  ;  treat  the  part  below  the  deck  in 
the  same  way.  Pin  a  stiff  flat  batten  to  these  spots,  and  run  lines  in. 
D*  the  mast  is  raked,  set  down  a  foot  on  perpendicular  A  X,  and 
place  the  rake  per  foot  on  perpendicular  X  Z  ;  and  from  this  point  Z 
draw  Z  A,  which  gives  the  cutting  line  for  the  heel.  The  head  is 
made  square  to  the  centre  line.  This  is  the  usual  method,  but  some 
shipbuilders  prefer  a  curve  with  less  pronounced  round. 

Expansion  of  the  Mast. — It  is  only  necessary  to  expand  one 
strake,  because  all  the  strakes  are  the  same  form.  Take  a  mast  with 
two  plates  in  the  round,  which  is  the  most  common.  It  is  evident 
that  each  strake,  if  overlapped  at  the  edges,  will  require  to  be  wider 
at  any  point  than  half  the  circumference  by  the  width  of  one  lap. 
Calculate  the  circumference  due  to  the  diameter  at  each  of  the  points 


.V  OF    I 


OF  CALlfO*^ 


IRON  AND  STEKL  MASTS.  91 


CHAPTER  XI. 

How  to  Obtain  the  Form  —Expansion  —Doubling  at  Deck — Doubling  at  Heel — 

Mast  Tube  Expansion. 


IRON  AND  STEEL  MASTS. 

Masts  are,  in  the  most  of  cases,  tapered  and  raked  aft,  the  rake 
varying-  from  \  to  2h  inches. 

To  Obtain  the  Form. — The  diameter  at  the  head  is  about  live- 
eighths  and  the  heel  about  three-fourths  of  the  deck  diameter.  Draw 
down  in  Fig.  86  a  straight  line  the  length  of  the  lower  mast,  on  a 
scale  of  \  inch  to  the  foot.  Let  this  line  A  B  be  the  centre,  and  on  it 
set  off  the  correct  positions  of  the  heel,  deck,  and  head.  The  housing 
is  best  measured  from  the  Sheer  Draught,  making  allowance  for 
camber  of  beam.  On  A  B,  produced  clear  of  the  heel,  describe  the 
circle  a  b  c,  with  diameter  equal  to  that  required  at  the  deck.  From 
the  points  a  and  c  describe  arcs  a  D  and  c  D  with  radii  a  c.  Find  a 
point  ef,  between  the  arcs,  equal  to  the  decided  diameter  at  the 
head.  Divide  G  H  into  a  suitable  number  of  equal  spaces,  say  four, 
and  level  lines  through  the  points  to  the  arcs.  Divide  the  distance 
on  the  line  A  B,  between  deck  and  head,  into  the  same  number  of 
equal  spaces  as  OH,  and  square  points  across  the  plan.  Lift  from 
the  section,  a  c,  op,  mn,gh,  and  ef,  around  G  H,  and  set  them  off 
on  their  corresponding  lines,  tfc1,  olpl,  in1  n1,  g1  h1,  and  e1/1,  divided 
equally  on  each  side  of  the  centre  ;  treat  the  part  below  the  deck  in 
the  same  way.  Pin  a  stiff  flat  batten  to  these  spots,  and  run  lines  in. 
If  the  mast  is  raked,  set  down  a  foot  on  perpendicular  A  X,  and 
place  the  rake  per  foot  on  perpendicular  X  Z  ;  and  from  this  point  Z 
draw  Z  A,  which  gives  the  cutting  line  for  the  heel.  The  head  is 
made  square  to  the  centre  line.  This  is  the  usual  method,  but  some 
shipbuilders  prefer  a  curve  with  less  pronounced  round. 

Expansion  of  the  Mast. — It  is  only  necessary  to  expand  one 
strake,  because  all  the  strakes  are  the  same  form.  Take  a  mast  with 
two  plates  in  the  round,  which  is  the  most  common.  It  is  evident 
that  each  strake,  if  overlapped  at  the  edges,  will  require  to  be  wider 
at  any  point  than  half  the  circumference  by  the  width  of  one  lap. 
Calculate  the  circumference  due  to  the  diameter  at  each  of  the  points 


92  NAVAL  ARCHITECTURE. 

or  at  the  butts,  and  half  the  quantity,  to  which  add  the  width  of 
one  lap.  Set  off  half  of  these  amounts  on  their  respective  points, 
at  each  side  of  the  centre  line  A1  B1,  drawn  parallel  to  A  B,  and  run 
curves  through  the  spots.  Make  allowance  for  the  length  of  the  heel 
in  each  strake  due  to  the  rake.  This  will  be  the  expansion  of  one 
strake  of  the  plating,  and  seeing  that  the  other  side  is  the  same, 
arrange  the  butts  for  both  strakes  on  this,  clear  of  each  other  and  of 
the  deck,  with  plates  of  equal  length,  except  the  ends ;  and  of  such  a 
length  that  they  can  be  got  into  the  special  yard  rolls.  Order  the 
plates  with  allowance  for  any  round  on  the  edge  of  the  expansion,  etc. 

Doubling  in  Way  of  the  Deck. — The  inside  strake  can  be 
doubled  on  the  outside,  and  the  outside  strake  on  the  inside  from 
edge  to  edge,  and  about  equal  lengths  below  and  above  the  deck ;  the 
extent  of  the  doubling  is  settled  by  the  Classification  Society. 

Doubling  on  the  Heel. — Seeing  this  is  usually  parallel  to  the 
foot  it  requires  expanding  to  get  its  true  form.  Fig.  87  shows  the 
doubling  on  the  foot  of  a  mast  with  considerable  rake  and  taper. 
Draw  in  the  centre  line  m a  and  ea,  so,  and  fl  square  to  it.  Then 
describe  a  circle  from  A  equal  to  ea,  and  from  B  equal  to//.  Divide 
the  circumference  of  each  into  8  equal  parts,  and  produce  the  points 
on  A  to  e  «,  and  on  B  to  /  /,  parallel  to  m  n.  Join  each  set  of  points, 
top  and  bottom,  and  produce  the  lines  on  to  et  and  fu.  From  the 
point  S  draw  level  line  q2  <f  equal  in  circumference  to  s  0,  and  divide 
it  into  8  equal  parts.  Erect  perpendicular  m1  n1.  Then  set  off  c-  r'2 
and  h2  h2,  with  vertical  distances  from  if  if  equal  to  s  e  and  s  I 
respectively,  and  set  on  c2  c2  about  m1  n1  the  circumference  of  e  a,  and 
on  h2h2  the  circumference  of  //.  Divide  each  into  8  equal  parts, 
and  join  the  corresponding  spots  on  the  three  lines,  which  produce 
above  c?c2  and  below  h2h2.  Measure  the  distances  of  the  top  of  the 
doubling  plates,  in  Fig.  87  above  ae  on  the  run  of  the  divisional  lines, 
and  set  them  on  their  respective  lines  in  the  expansion  above  <?<?,  and 
those  for  the  bottom  below  h2h2.  Run  curve  through  the  spots  and 
you  have  a  complete  expansion  of  the  doubling  plate.  This  plate 
may  be  ordered  in  two  pieces. 

Expansion  of  a  Mast  Tube. — In  Fig.  88,  A  B  C  D  is  the  mast 
tube.  Make  D  E  square  to  D  C.  Produce  centre  of  the  mast  and 
from  F  as  centre  describe  circle  of  diameter  D  E.  Divide  circum- 
ference into  say  8  equal  parts  in  the  points  1,  2,  3,  etc.,  and  produce 
these  parallel  to  the  centre  on  to  lines  D  B  and  0  A.  Extend  D  E  to 
1,  and  AG  parallel  to  D  E,  produced   into  the  expansion.      Girth 


Sftcioa 


IRON  AND  STEEL  MASTS.  95 

circle  from  1  for  the  position  of  2,  3,  4,  5,  6,  7,  8  relative  to  1,  and 
lay  them  off  in  the  expansion  on  D  E,  produced,  from  1.  Erect 
perpendiculars  at  the  points  to  cut  top  line  A  Gr  continued.  Produce 
points  l1,  21,  31,  41,  51,  61,  71,  and  81,  parallel  to  DE  until  they  cut 
their  corresponding  lines  in  the  expansion.  Of  course  it  will  be 
evident  that  21  and  81,  31  and  71,  41  and  61  are  duplicate  and  in  the 
same  line.  Repeat  the  process  for  the  top  of  the  tube.  Then  the 
figure  H,  K,  L,  M,  N,  0,  is  the  developed  form  of  the  plate  for 
the  tube.  It  is  usual  to  make  these  tubes  in  one  plate,  and  welded  at 
the  butt,  so  that  an  allowance  of  about  1  inch  should  be  given  for 
that  purpose.     The  sketch  plate  may  be  ordered  to  prevent  waste. 

It  may  be  noted  that  the  amount  of  wedging  varies  from  about 
\\  to  2|  inches. 


96  NAVAL  ARCHITECTURE. 


CHAPTER  XII. 

Rudder  Trunk  —Expansion  of  the  Trunk— Iron  Deck-house —Expansion  of  the 
Corner  Plate— Cargo  Hatch  Coamings —Cargo  Hatch  Coamings  with 
Bell-mouth  Bottoms -Marking  off  the  Hawse-pipes— Shaft  Tunnel  of  a 
Single  Screw  —Expansion  of  the  Tunnel  Plating— Calculation  for  Ex- 
pansion— Marking  off  the  Freeboard— Finding  the  Depth  Moulded  at 
the  Ship  when  Dry — Finding  the  Depth  Moulded  when  the  Ship  is 
Afloat — Clipper  Stem  or  Cutwater  -End  of  the  Stem  Bar  or  Figure 
Step— Back  of  Stem  for  Lacing-piece —Figure  Head  Moulds — Forecastle 
Head — Setting  off  the  Draught  Marks  on  the  Stem  and  Stern  —To  Form 
an  Oval  Manhole— Another  Method. 


MISCELLANEOUS. 

There  are  several  items  which  are  developed  either  in  the  drawing- 
office  or  on  the  loft  floor,  and  yet  cannot  be  rightly  classed  under  the 
term  "  laying-off."  The  most  important  of  these  we  shall  now  consider 
in  this  chapter. 

Rudder  Trunk. — This  trunk  is  made  of  steel  plate,  and  should  be 
sufficiently  large  to  allow  the  rudder  to  go  into  position  easily,  without 
disturbing  the  structure.  In  Fig.  89  draw  rudder  in  the  working 
position,  and  then  make  an  outline  tracing  and  place  it  in  the  dotted 
position,  so  that  the  top  pintle  P  will  clear  the  gudgeon  when  shipping, 
and  the  stock  the  deck  at  B  ;  and  draw  in  the  after  edge  of  the  trunk 
C  D  to  suit  this.  There  are  two  ways  of  construction,  arising  out  of 
different  methods  of  fitting  the  transom  floor  :  where  the  floor  is  on 
the  fore  side  of  the  stern  post,  as  in  Fig.  91,  the  trunk  is  lapped  on  to 
the  stern  post,  but  where  the  floor  is  on  the  after  side  of  the  post  its 
centre  is  carried  up  to  the  deck  sufficiently  wide  to  take  the  trunk. 
Fig.  91  is  an  enlarged  sketch  of  Fig.  89. 

Expansion  of  the  Trunk. — In  Fig.  90,  square  E  to  E1,  and 
extend  to  E2 ;  produce  I)1  C1  to  C2 ;  make  E1  C2  and  F  D1  square  to 
D'C1.  Draw  suitable  section  of  bottom,  with  outstretch  E2C2 :  and 
a  section  for  top,  with  outstretch  F  D1.  The  width  will  be  decided 
by  the  size  of  the  attaching  bars.  Fix  points  h  and  c  in  the  bottom 
section ;  then  girth  the  section  for  b,  a,  and  c  relative  to  the  floor, 
and  lay  the  widths  out  on  E3  and  E2.  Through  a1  erect  perpendicular 
for  the  centre  of  the  expansion.  Lift  the  height  of  the  trunk  above 
C2  E1    on  b2,   and  lay  it   off  on   the   expansion   above   bl   and   c1. 


o 

0) 


MISCELLANEOUS. 


99 


Measure  the  length  of  C2  "D1  with  the  point  C1  from  C2,  and  lay 


them  off  on  the  centre  above    E3  E2. 


Pass  a   curve    through   the 


0) 

L 


points,  which  will  give  form  of  the  bottom  edge.     The  point  D2  will 
be  the  extreme  length  of  the  plate,  and  the  level  for  the  points  F1 


100  NAVAL  ARCHITECTURE. 

will  be  got  by  girthing  the  top  section  around  the  centre  line,  and 
setting-  them  off  each  side  of  D2.  The  distance  of  the  trunk  top,  on 
the  centre  below  I)2,  may  be  got  from  D1  in  the  fore  and  aft  section, 
and  measuring  it  down  in  the  expansion.  Through  the  three  points 
run  the  curve  of  the  top  edge. 

The  expansion  of  Fig.  91  is  got  in  a  similar  manner.  Draw  circular 
sections  in  for  top  and  bottom,  with  respective  outstretch  of  F  D1 
and  E1  C2.  Mark  points  a,  b,  c  in  the  section.  Girth  the  bottom 
section,  and  lift  points  d,  b,  a,  c,  and  d1,  and  lay  them  out  on  ds  d2. 
Erect  perpendicular  through  a1.  Lift  distance  above  C2  E1  to  the 
edge  of  the  trunk  in  fore  and  aft  section,  and  transfer  them  to 
their  corresponding  points  in  the  expansion  for  the  form  of  the 
bottom.  Lift  (Pl&nd  D1  above  C2,  and  set  them  on  the  expansion 
centre  above  d3d2;  then  D2  will  give  level  heights  for  F1  and  F2. 
Girth  the  top  section  around  a1,  and  lay  the  girths  on  each  side  of  Da 
on  F1  F2.  The  distance  of  the  centre  below  D2  will  be  got  in  the  fore 
and  aft  section  below  D1.  Join  F1  to  d3,  and  F2  to  d'2,  and  you  have 
form  of  the  plate. 

Iron  Deck = house. — In  Fig.  92,  show  side  and  end  elevations 
with  corner  plates  carried  the  full  depth,  and  having  a  radius  of 
about  9  inches.  Arrange  the  coaming  plates  of  suitable  height  for 
door  step,  and  place  a  plate  on  the  top  edge  about  9  inches  deep. 
These  plates  are  all  flush  and  strapped  on  the  inside.  The  inter- 
mediate plates  A  are  set  in  and  lapped  on  to  corners  and  top  and 
bottom  plates,  and  made  flush  at  the  other  butts  with  pilasters  on 
the  outside  forming  straps.  The  pilasters  are  placed  to  suit  doors 
and  windows.  This  arrangement  makes  a  substantial  and  good 
looking  job  when  properly  considered.  The  size  of  the  straight  plates 
may  be  easily  measured  off,  but  in  the  case  of  considerable  sheer,  care 
must  be  taken  to  allow  for  it  in  the  length  of  the  plates.  The  ordered 
length  of  the  corner  plates  will  be  C  in  the  figure,  while  the  girth 
may  be  calculated.     "With  a  radius  of  9  inches  the  width  would  be 

3-1416  x  18"  +ab  +  dei&mn  incheS)  -  u"-14  +  6"  +  6"=  2 0"^ full ; 

a  little  is  allowed  for  planing. 

Expansion  of  the  Corner  Plate. — In  Fig.  92.     Erect  centre 

line  gj\  and  draw  in  h  I1  and  lhl  parallel  to  the  centre  and  each  equal 

14'*14  26'"14 

in  distance  to  -       -  and  m1  n1  and  m  n  parallel  and  each  equal  to  " 

2t  £ 

from  the  centre.     Square  up  d  into  the  elevation,  and  produce  0  to 


Fiar;  92. 


DECK    HOUSE 


ION 


TV 


_u 


h 


w 


J&. 


->\ 


I    I 


>r 


_io ^ 


• 


JRVE 


FORWARD 


Fisr.  92. 
DECK    HOUSE. 


FORE    8c    AFT     ELEVATION 


END     ELEVATION 


EXPANSION 
OF  CORNER    PLATE 


K_  Ik  . 


=TF~ 


i! 


LT 


n 


!5"|_J 


X 


M 


w 


js: 


T^ 


HALF       PLAN 


CENTRE       LINE      OF    SH(P 


FORWARD 


LONQITUDINAL     ELEVATION 


*— £■ 


PLAN 


CARCO        HATCH 


CENTRE 


CALlvO^ 


LONGITUDINAL      ELEVATION 


i   i 


I    1|    | 

Li...' 


*M^ 


PLAN 


DECK, 

CENTRE 


I 


CARGO        HATCH 


CENTRE 


Fig.  93. 
CARGO    HATCH. 


EXPANSION  OF    END    PLATES 
3l . 


LONQITUDINAL      ELEVATION 


J. 


fc=fc 


PLAN 


CARCO        HATCH 


CENTRE 


_L_ 


DECK. 


MISCELLANEOUS.  101 

m1,  which  will  give  point  on  Ih1.  Then  set  off  a,  b,  and  c  on  the 
camber  curve  and  lift  the  height  above  the  base  oml.  Set  c  above 
m1  m  on  gf,  and  b  on  A/1,  and  a  on.  mlnx.  A  curve  passed  through 
the  points  p,  w,  x,  J,  m  will  give  the  form  of  the  bottom  edge  of  the 
plate.  If  the  house  top  has  the  same  camber  as  the  deck  then  set 
m1p  below  n,  and  wh  below  A1,  and  gx  below  f,  and  make  n1  I  parallel 
to  I  m.  A  curve  through  the  spots  gives  top  edge.  Then  you  have 
expanded  form  of  the  plate.  Considerable  shee..  on  the  deck  would 
make  a  difference,  but  if  the  elevation  is  rightly  drawn  down  it  will 
be  readily  seen. 

Cargo  Hatch  Coamings. — In  Fig.  93,  draw  the  hatch  in  plan, 
and  arrange  butts,  e,  of  the  plating,  so  that  the  strap  will  clear  beam 
and  corner  round.  The  corners  are  drawn  to  about  twelve  inch 
radius.  Get  out  transverse  form  of  the  deck  from  the  camber  curve 
and  set  off  width  of  the  hatch  each  side  of  the  centre,  from  which, 
above  the  deck  curve,  erect  perpendiculars,  a1  b1  and  a  b,  equal  to 
the  height  at  the  sides.  Eun  in  curve  b1  d  b  with  a  round  up  of 
about  6  inches  from  the  points  b  and  b1.  The  sides  a  b  and  a1  b1 
should  extend  below  the  half  beams  about  \  inch.  The  end  plates 
E  are  carried  down  over  //  (in  plan)  to  the  top  of  the  bulb  of  the 
through  beam,  and  then  dropped  to  meet  the  side  plates  at  the  butts. 
Next  show  in  longitudinal  elevation  from  the  plan  and  cross  section, 
and  square  up  from  the  plan  the  butts  e.  The  size  of  the  side  plates 
may  be  measured  from  this  plan  ;  should  there  be  any  sheer  a  little 
must  be  allowed  on  the  lengths  to  meet  it.  The  expansion  of  the  end 
plates  E  may  now  be  drawn  in.  Set  off  the  depth  dg  on  the  centre 
line  of  the  expansion,  dx  gl,  and  the  form  of  the  top/2  d1  f2  =f1  dj  \ 

Calculate    the    girth    of    the    corner    from   f  to   h  =— 

4: 

=  18"-8496,  say  1'  7".  Measure  it  off,  on  each  side,  parallel  to/2  /3, 
shown  by  dotted  line  h1  and  h2  ;  add  to  it  parallel  distance  h  e 
measured  from  the  plan.  The  depth  el  0  and  e2  0  is  made  equal  to  the 
depth  at  the  sides,  and  is  carried  in  parallel  to  bottom  edge  over  A1  el 
and  e2  h2,  and  run  in  gradually  to  meet  top  curve.  The  bottom  edge  is 
recessed  between/3  /3.  The  depth  at  f2  ps  =fl  p,  d}  p6  =  dpi  and 
/2  p1  =/x  p1.  This  is  owing  to  end  plate  over  //  stopping  at  the 
top  edge  of  the  beam  bulb.  Sketch  plates  may  be  ordered  from  this 
expansion  to  form  the  hatch  ends,  together  with  double  riveted  butt 
straps.  Sometimes  the  hatch  is  made  broader,  across  b1  b  than  a1  a 
by  about  1^  inches  for  shipping  and  unshipping  hatch  beam.  In 
that  case  e1 0  would  not  be  parallel  to  d1  g\ 


"^>        OF 


OF  CALlfO**^ 


MISCELLANEOUS.  101 

m1,  which  will  give  point  on  Ih1.  Then  set  off  a,  b,  and  c  on  the 
camber  curve  and  lift  the  height  above  the  base  oml.  Set  c  above 
mlm  on  gf,  and  b  on  A/1,  and  a  on  mlnx.  A  curve  passed  through 
the  points  p,  w,  x,  1,  m  will  give  the  form  of  the  bottom  edge  of  the 
plate.  If  the  house  top  has  the  same  camber  as  the  deck  then  set 
mlp  below  n,  and  wh  below  A1,  and  gx  below  f,  and  make  n1 1  parallel 
to  I  m.  A  curve  through  the  spots  gives  top  edge.  Then  you  have 
expanded  form  of  the  plate.  Considerable  shee..  on  the  deck  would 
make  a  difference,  but  if  the  elevation  is  rightly  drawn  down  it  will 
be  readily  seen. 

Cargo  Hatch  Coamings. — In  Fig.  93,  draw  the  hatch  in  plan, 
and  arrange  butts,  p,  of  the  plating,  so  that  the  strap  will  clear  beam 
and  corner  round.  The  corners  are  drawn  to  about  twelve  inch 
radius.  Get  out  transverse  form  of  the  deck  from  the  camber  curve 
and  set  off  width  of  the  hatch  each  side  of  the  centre,  from  which, 
above  the  deck  curve,  erect  perpendiculars,  a1  bl  and  a  b,  equal  to 
the  height  at  the  sides.  Run  in  curve  bl  d  b  with  a  round  up  of 
about  6  inches  from  the  points  b  and  b1.  The  sides  a  b  and  a1  bl 
should  extend  below  the  half  beams  about  |  inch.  The  end  plates 
E  are  carried  down  over  //'  (in  plan)  to  the  top  of  the  bulb  of  the 
through  beam,  and  then  dropped  to  meet  the  side  plates  at  the  butts. 
Next  show  in  longitudinal  elevation  from  the  plan  and  cross  section, 
and  square  up  from  the  plan  the  butts  e.  The  size  of  the  side  plates 
may  be  measured  from  this  plan  ;  should  there  be  any  sheer  a  little 
must  be  allowed  on  the  lengths  to  meet  it.  The  expansion  of  the  end 
plates  E  may  now  be  drawn  in.  Set  off  the  depth  dg  on  the  centre 
line  of  the  expansion,  dl  gl,  and  the  form  of  the  top/2  d1/2  =/1  d  J  \ 

Calculate    the    girth    of    the    corner   from    f  to   h  =- 

to  J  4. 

=  18"'8496,  say  1'  7".  Measure  it  off,  on  each  side,  parallel  to/2  /3, 
shown  by  dotted  line  A1  and  A2  ;  add  to  it  parallel  distance  A  e 
measured  from  the  plan.  The  depth  e1  0  and  e2  0  is  made  equal  to  the 
depth  at  the  sides,  and  is  carried  in  parallel  to  bottom  edge  over  A1  e1 

.  and  e2  A2,  and  run  in  gradually  to  meet  top  curve.  The  bottom  edge  is 
recessed  between/3  /3.     The  depth  at  /2  p3  =/1  p,  d1  ]>5  =  dp4-  and 

f2  f"  —f1  P1-  This  is  owing  to  end  plate  over  //  stopping  at  the 
top  edge  of  the  beam  bulb.  Sketch  plates  may  be  ordered  from  this 
expansion  to  form  the  hatch  ends,  together  with  double  riveted  butt 
straps.  Sometimes  the  hatch  is  made  broader,  across  bl  b  than  a1  a 
by  about  1|  inches  for  shipping  and  unshipping  hatch  beam.  In 
that  case  e1 0  would  not  be  parallel  to  d1  g\ 


102  NAVAL  ARCHITECTURE. 

Cargo  Hatch  Coamings  with  Bell  =  mouth  Bottoms. — 
In  Fig.  94,  sketch  in  the  hatch  as  before,  only  with  suitable  bell 
mouth  on  the  lower  edge  as  shown  in  the  plan  by  the  dotted  lines 
a,  b,  c,  and  d.  The  corner  plates  are  butted  on  the  ends  rm,  and  on 
sides  s  n,  to  allow  them  to  be  easily  "blocked"  into  shape.  The 
expansion  of  the  end  plates  may  be  got  by  girthing  e  /',  and  setting 
it  off  on  the  cross  section/1  e\  the  bottom  line  being  made  parallel  to 
g  h.  Then  he^gf1  r1  is  the  expanded  plate.  The  side  plates  are 
got  by  girthing  Ice  and  setting  it  off  in  the  longitudinal  elevation 
k1  P  and  k2 t2,  then  Jcl  I1  t2  Jc~  is  the  expansion.  The  corner  plates 
will  need  more  careful  attention.  Girth  the  length  on  fe,  from 
the  point  >•'  squared  over,  for  t  and  c,  and  lay  them  out  on  the 
expansion  centre  line  from  rl  s1.  Square  down  t  into  the  plan,  and 
draw  in  through  the  point  quadrant  of  a  circle  op.  Then  girth,  in 
the  plan,  around  the  centre  of  the  corner  mn,  oy,  rs,  and  set  these 
on  their  corresponding  lines  in  the  expansion  m1  n\  olpl,  r2  s1.  Produce 
the  heights  from  the  cross  sections  to  meet  and  you  have  spots  for 
the  form  of  the  expanded  plate.  A  few  extra  points  between  /•  s 
would  enable  you  to  get  the  top  edge  more  accurately. 

Marking  off  the  Hawse  =  pipes. — Indicate  on  the  forecastle 
deck  the  lead  of  the  cable  from  the  windlass,  and  settle  the  position 
of  the  centre  of  the  pipe  on  the  forecastle  deck  to  clear  beams, 
through  which  make  a  hole  about  6  inches  square  and  drop  a 
plumb-line  from  it.  Fix  the  position  of  the  centre  of  the  pipe  on 
the  shell,  by  continuing  the  plumb-line  distance  parallel  to  the  centre 
of  the  ship,  and  in  such  a  position  that  the  stringer  bar  remains 
undisturbed  and  only  one  frame  to  cut.  Cut  a  hole  at  this  point 
in  the  shell  about  4  inches  square.  Obtain  a  straight  round  bar, 
about  lj  inches  in  diameter,  long  enough  to  reach  from  the  fore- 
castle hole  to  that  of  the  shell,  and  secure  it  by  wedges  in  position 
at  the  propei'  distance  from  the  centre  line.  Make  a  piece  of  wood, 
say  2  inches  thick,  of  the  form  A,  shown  in  Fig.  95,  and  of  radius 
I)  equal  to  half  the  diameter  of  the  outside  of  the  pipe.  Hollow 
one  edge  of  the  wood  to  fit  the  bar,  chalk  the  point  C  and  slide 
it  round  the  bar,  so  that  C  will  touch  the  shell.  By  this  means 
the  correct  shape  of  the  hole  required  will  be  secured.  Reverse  the 
piece  A,  and  do  the  same  witli  the  forecastle  deck.  Take  the  bar  out 
of  position  and  cut  the  holes;  which  should  be  made  slightly  larger 
for  the  easy  shipment  of  the  pipe.  A  circular  pipe  mould,  sufficiently 
long  to  reach  beyond  the  holes,  is  then  placed  in  position ;  that  of  the 


LONGITUDINAL      ELEVATION 


1 


PLAN      OF 
CARGO      HATCH 


\ 


\ 


"■*1 


■-WV-, 


/ 


a, 


s       x 


Fig.   94. 
BELL-MOUTH    CARGO    HATCH. 


END    ELEVATION 
-iL 


EXPANSION    OF 
CORNER     PLATE 


LONGITUDINAL      ELEVATION 


IT' 
l.j-1 


i:-: 


■-DEC  is 


JL 


PLAN     OF 
CARGO      HATCH 


\ 

\ 

H 


J 


T~     • 


MISCELLANEOUS. 


103 


shell  is  cut  flush  and  a  ring  mould  for  shell  flange  screwed  on  to  the 
end.  It  may  be  noted  that  this  mould  is  shipped  into  position  from 
the  outside  of  the  vessel,  and  has  a  slight  taper  on  the  end  put  in  first. 
When  in  position  a  thin  layer  of  lead  is  tacked  on  the  forecastle  deck 
end,  to  show  the  line  of  the  deck  all  round,  which  is  the  correct 
length  ;  it  is  then  drawn  out  and  sent  away  to  the  foundry  for  casting 
the  pipe. 

Shaft  Tunnel  of  a  Single  Screw. — The  shaft  is  cased  in  from 
the  engine  room  to  the  after  stuffing-box  bulkhead,  forming  a  tunnel ; 
so  that  it  is  accessible  to  the  engineers  at  all  times.     Get  out  a  plan  and 

Fig.   95. 


/ 

elevation  on  £  inch  scale  as  in  Fig.  96,  showing  the  floors  and  tank 
top  between  the  bulkheads.  Set  off  at  each  bulkhead,  in  the  elevation, 
the  height  of  the  centre  of  shaft  and  draw  line  in.  Arrange  thrust 
recess  at  the  fore  end,  in  plan  and  elevation,  usually  of  box  form.  The 
tunnel  crown  just  forward  of  the  after  bulkhead  is  attached  to  the 
side  stringers,  and  an  additional  partial  bulkhead  is  fitted,  G-  H, 
extending  to  ship's  side,  against  which  the  form  from  C  to  D 
terminates,  and  enables  a  better  connection  to  be  made,  and  leaves 
more  room  to  get  at  the  stuffing-box.  Set  off  height  of  tunnel  at  the 
ends  F  C  and  E  B,  and  connect  C  to  D.  Then  draw  in  plan  the  sides 
of  the  tunnel  from  C  to  D.  The  passage  way  is  shown  on  the  star- 
board side  of  the  centre.  Arrange  the  stiffeners  ;  which  may  be  on 
the  out  or  inside — they  are  shown  inside.     The  spacing  is  4  feet,  but 


MISCELLANEOUS. 


103 


shell  is  cut  flush  and  a  ring  mould  for  shell  flange  screwed  on  to  the 
end.  It  may  be  noted  that  this  mould  is  shipped  into  position  from 
the  outside  of  the  vessel,  and  has  a  slight  taper  on  the  end  put  in  first. 
"When  in  position  a  thin  layer  of  lead  is  tacked  on  the  forecastle  deck 
end,  to  show  the  line  of  the  deck  all  round,  which  is  the  correct 
length  ;  it  is  then  drawn  out  and  sent  away  to  the  foundry  for  casting 
the  pipe. 

Shaft  Tunnel  of  a  Single  Screw. — The  shaft  is  cased  in  from 
the  engine  room  to  the  after  stuffing-box  bulkhead,  forming  a  tunnel ; 
so  that  it  is  accessible  to  the  engineers  at  all  times.     Get  out  a  plan  and 

Fig.   95. 


elevation  on  £  inch  scale  as  in  Fig.  96,  showing  the  floors  and  tank 
top  between  the  bulkheads.  Set  off  at  each  bulkhead,  in  the  elevation, 
the  height  of  the  centre  of  shaft  and  draw  line  in.  Arrange  thrust 
recess  at  the  fore  end,  in  plan  and  elevation,  usually  of  box  form.  The 
tunnel  crown  just  forward  of  the  after  bulkhead  is  attached  to  the 
side  stringers,  and  an  additional  partial  bulkhead  is  fitted,  G  H, 
extending  to  ship's  side,  against  which  the  form  from  C  to  D 
terminates,  and  enables  a  better  connection  to  be  made,  and  leaves 
more  room  to  get  at  the  stuffing-box.  Set  off  height  of  tunnel  at  the 
ends  F  C  and  E  D,  and  connect  0  to  D.  Then  draw  in  plan  the  sides 
of  the  tunnel  from  C  to  D.  The  passage  way  is  shown  on  the  star- 
board side  of  the  centre.  Arrange  the  stiffeners  ;  which  may  be  on 
the  out  or  inside — they  are  shown  inside.     The  spacing  is  4  feet,  but 


104 


NAVAL  ARCHITECTURE. 


in  way  of  the  cargo  hatches  they  are  required  to  be  3  feet.  Those  on 
forward  recess  are  the  same  spacing  as  the  ship's  framing.  Show 
stools,  etc.,  in  position. 

Expansion  of  the  Tunnel  Plating. — The  forward  recess  is 
easily  marked  off.  Get  out  a  section  through  A  B,  arrange  laps, 
flanging  the  plates  as  shown  at  the  sides.  Girth  this  section,  around 
the  centre  of  the  tunnel,  at  the  forward  and  after  ends,  and  set  off  the 
widths  in  the  expansion  at  each  side  of  the  centre,  and  draw  lines  in. 

The  part  from  C  to  I)  needs  more  care.  Calculate  the  circum- 
ference of  a  circle  of  diameter  equal  to  the  width  of  the  tunnel,  that 
is,  2  a,  and  half  what  you  get  will  be  the  girth  of  the  circular  part ; 
then  add  on  for  the  after  end  sides  c  b  +  fd,  which  is  the  total  girth 
without  laps ;  the  forward  end  will  be  found  by  adding  to  the  circular 
girth  eg  +fe.  These  total  dimensions  are  laid  off  at  their  respective 
ends  in  equal  halves,  at  each  side  of  the  centre  of  tunnel,  which  will 
give  the  expansion  of  form  from  C  to  1). 

A  lap  is  placed  at  the  centre  of  the  tunnel  as  shown,  and  the 
others  are  arranged  so  that  the  two  side  plates  do  not  require  any 
round.  In  other  words  laps  marked  o  and  p  in  the  section  are  kept 
below  c  and/. 

Calculation  for  Expansion  Width  at  C  F  and  E  D. — Height 

at  0  F  =  7  feet  9  inches,  E  D  =  7  feet  3  inches.     Tunnel  4  feet  wide. 

„.         .  .    .      ,  ,4  feet  x  3-141G       12'5664 

Circumference  of  circular  part  to  cj  —  -        —-—        -  =      — —     = 

Then  girth  at  E  1). 

Circular  part 

Lower  part  2  (7'  3"  — 

2'  0")  =  5'  3"  x  2 
Laps  3  x  2^" 

Total  girth  of  plating         18'  4|"     Total  girth  of  plating 

Marking  off  the  Freeboard. — Fig.  97  is  the  marking  lor  a 
steamer,  and  Fig.  98  for  a  sailing  ship.  The  disc  and  lines  must  be 
permanently  indicated  by  centre  punch  marks  or  cutting.  The  centre 
of  the  disc  is  required  to  be  placed  midway  between  the  perpen- 
diculars of  the  load-line  on  each  side  of  the  vessel.  It  is  difficult  to 
exactly  state  a  method  for  marking  it  off  on  the  ship,  for  ships  vary 
so  much  in  their  construction.  One  method  is  to  place  a  deal,  levelled, 
on  top  of  the  sheer  strake  (see  Fig.  99),  and  drop  a  plumb-line  from  it. 


6-2832  feet  =  G  feet 

°8 

inches 

1. 

Then  girth  at  C  F. 

Circular  part 

=    6' 

o3" 
°8 

Lower  part  2  (7'  9"  - 

2'  0")  =  5'  9"  x  2 

=  11' 

6" 

Laps  3  x  2h" 

= 

71" 

'  2 

=    G' 

°8 

=  10' 

6" 

= 

i-»  1  » 
'2 

17' 

4.1" 

*8 

(AT!  ON 


pNNEL 


ER       B, 


E OF 


UM 


SECTION  OF  TUNNEL  FROM  C  TO  0 
LOOKING    FORWARD 


c 

0 

r 

! 
i 

/ 

r 

6 

... 

i 
i 

_,L_. 

t 

\                    * 

v;> 

atCIIONAL       LLhVAMUN                                     TUNNEL     PLAN                                 Fig     96. 

ECT  '-■     '    - 
LOOKINC   . 

-  c 

A 

f 

CENTRE 

OF 

SHAFT 

i ^-J 

'         1 

3  _ 

1 

i 

I         i 



TUNNEL 

/ 

1  ' 

i 
1 

F 

WAT 

ER 

BALLAST 

E 

Bh 

B 

BH 

1 

AFT_ 


I  STOOL 


PLAN 


CENTRE       OF      SHAFT 


'STOOL 


THRUST    BLOC 


RECESS 


FORWARO 


EXPANSION 


Fig.  97. 


VL 


_  4 


SD 


Fig.   98. 


WNA 


S  D    =  Top  of  Statutory  Deck  Line. 
F       =  Freeboard. 

U  E  =  Upper  Edge  of  Horizontal  Line  passing  through  Centre  of  Disc. 
V  L  =  21  Inches. 

OD  =  Outside  Diameter  of  Disc,  12  Inches,  1  Inch  Thick. 
H  L  =  Horizontal   Line  18  Inches  Long  and  1  Inch  in  Thickness. 
L       =9  Inches  Long  and  1  Inch  Thick. 

C        =  These  Dimensions  to  be  taken  from  Centre   of   Disc  to   Top  of 
each  Line. 


/0\ 


LlBRA^p 


OF  IBS 


tmrvEg 


WNA 


SD    =  Top  of  Statutory  Deck  Line. 
F       =  Freeboard. 

U  E  =  Upper  Edge  of  Horizontal  Line  passing  through  Centre  of  Disc. 
V  L  =  21  Inches. 

0  D  =  Outside  Diameter  of  Disc,  12  Inches,   1  Inch  Thick. 
H  L  =  Horizontal   Line  18  Inches  Long  and  1  Inch  in  Thickness. 
L       =  9  Inches  Long  and  1  Inch  Thick. 

C        =  These  Dimensions  to  be  taken  from  Centre   of   Disc  to   Top  of 
each  Line. 


106 


NAVAL  ARCHITECTURE. 


Mark  on  side  plating  the  depth  moulded  line  B,  and  above  it  indicate 
the  statutory  deck  line  S  D.  Measure  the  height  from  S  D  to  the 
deal  and  add  it  to  the  required  freeboard.  Mark  this  on  a  straight 
batten,  and  set  it  below  the  deal  on  the  plumb-line,  and  square  the 
point  on  to  the  shell,  which  will  give  the  centre  of  the  disc. 

Finding  the  Depth  Moulded  at  the  Ship  when  dry. — This 
is  done  when  the  vessel  is  on  the  yard,  or  in  dry  dock,  by  fixing  a  deal 

Fig,  99. 


or  straight  edge  as  A  B  in  Fig.  ioo,  under  the  keel  athwai'tships  in 
way  of  the  midship  frame,  and  one  above  it  on  the  top  of  the  sheer 
strake  edges  C  D.  Drop  a  plumbed  tape  line  from  the  top  deal,  clear 
of  the  side,  and  measure  the  depth  between  the  inside  edges  of  the 
deals  on  each  side  of  the  vessel.  Deduct  the  height  of  the  sheer 
strake  above  the  beams  and  the  depth  of  the  keel  from  each,  and  add 
the  remaining  quantities  together,  then  half  the  addition  will  be  the 
depth  moulded. 

Finding  the  Depth  Moulded  when  the  Ship  is  afloat. — 
Fix  a  deal  across  the  ship  at  the  midship  frame  on  the  top  of  the 
sheer  strakes  or  rail.  Measure  the  plumbed  distance  from  the  under 
side  of  the  deal  to  the  water  on  each  side  of  the  vessel,  and  deduct  the 
height  of  the  sheer  strake  from  the  top  of  the  beams  in  each  case.    To 


Fig.    101 


MISCELLANEOUS. 


107 


the  remaining  quantities  add  the  mean  draught,  less  the  depth  of  the 
keel,  then  half  the  sum  of  these  will  be  the  depth  moulded.* 

Clipper  Stem  or  Cut= water.— The  arrangement  is  very  much  a 
subject  of  taste,  etc.,  but  Fig.  101  is  given  as  near  as  possible  on  the 
lines  of  modern  ideas.  Draw  in  the  lower  moulding  C  1)  of  the  trail- 
board,  which  is  a  continuation  of  the  gunwale  moulding,  and  made  of 
hard  wood.     It  should  terminate  on  the  foot  of  the  figure  about  the 

Fig.   100. 


step  AB.  Run  in  the  top  moulding  EF,  lifting  it  up  to  form 
the  crown  of  the  figure  and  cutting  the  rail  line  G  H  at  H,  produced 
to  the  correct  sheer  Then  draw  in  the  profile  of  the  figure  The 
bowsprit  should  be  shown  in  position  to  clear  the  figure  by  about  2 
inches.  The  forecastle  head  is  usually  made  a  continuation  of  the 
part  of  the  stem  just  above  the  load-line. 

End  of  the  Stem  Bar  or  Figure  Step.— The  bobstay  eye  is 
put  on  the  end  of  the  stem  bar,  which  should  terminate  in  such  a 

*  The  mean  draught  is  half  the  sum  of  the  forward  and  after  draughts. 


&■        r\v  THR 


OF  THR 


UNIVERSITY 


MISCELLANEOUS. 


107 


the  remaining  quantities  add  the  mean  draught,  less  the  depth  of  the 
keel,  then  half  the  sum  of  these  will  be  the  depth  moulded.* 

Clipper  Stem  or  Cut= water. — The  arrangement  is  very  much  a 
subject  of  taste,  etc.,  but  Fig.  101  is  given  as  near  as  possible  on  the 
lines  of  modern  ideas.  Draw  in  the  lower  moulding  C  I)  of  the  trail- 
board,  which  is  a  continuation  of  the  gunwale  moulding,  and  made  of 
hard  wood.     It  should  terminate  on  the  foot  of  the  figure  about  the 

Fig.  IOC. 


step  A  B.  Run  in  the  top  moulding  E  F,  lifting  it  up  to  form 
the  crown  of  the  figure  and  cutting  the  rail  line  Gr  H  at  H,  produced 
to  the  correct  sheer  Then  draw  in  the  profile  of  the  figure  The 
bowsprit  should  be  shown  in  position  to  clear  the  figure  by  about  2 
inches.  The  forecastle  head  is  usually  made  a  continuation  of  the 
part  of  the  stem  just  above  the  load-line. 

End  of  the  Stem  Bar  or  Figure  Step. — The  bobstay  eye  is 
put  on  the  end  of  the  stem  bar,  which  should  terminate  in  such  a 

*  The  mean  draught  is  half  the  sum  of  the  forward  and  after  draughts. 


108 


NAVAL  ARCHITECTURE. 


Fig.  102. 


position  that  the  stay  when  fixed  will  clear  the  front,  and  yet  allow 
sufficient  for  forming  figure  of  6  to  8  feet  long.  This  will  decide  the 
step  A  B,  which  is  made  square  to  the  cut-water  and  extends  back  to 
B,  about  i)  inches  clear  of  the  stem  bar. 

Back  of  Stem  for  Lacing= piece. — From  the  point  B,  in  Fig. 
104,  draw  BH  a  straight  line  to  give  about  22  inches  across  the 

figure  at  J  K.  The  side  plating  pro- 
jects forward  of  B  H  about  2  inches, 
as  shown  in  sectional  Fig.  102,  and 
the  distance  a  b  should  be  about  8 
inches  for  the  full  depth  of  B  H,  or 
slightly  tapered  towards  B.  A  plate 
is  fitted  to  form  back,  being  flanged 
to  take  side  plating  and  bent  round 
at  foot  to  form  the  step  AB,  upon 
which  is  fitted  a  shoe,  as  in  Fig.  103, 
which  takes  the  shell  and  is  attached 
with  a  tap  to  the  stem  head,  and 
serves  for  stepping  the  figure  foot 
into.  A  lacing-piece  of  1^  inch  pine 
is  attached  to  the  back  plate  B  H 
for  the  full  depth.  The  figure  is 
fixed  by  passing  bolts,  from  the  front,  through  the  back  plate  with 
nuts  on  the  inside. 

Figure  Head  Moulds.— The  form  of  the  trail  board  is  painted 
on  the  ship  to  please  the  eye,  and  a  mould  made  therefrom  embracing 
top  rail,  which  is  sent  to  the  carver,  together  with  one  for  the  depth 
and  length  of  the  block,  and  one  for  the  shape  of  the  lacing-piece  and 
step. 

The  trail-boards  are  made  about  4  inches  thick  to  begin  with,  so 
that  the  figure-block  should  be  about  16  inches  wide.  This  is  cut 
down  in  thickness  in  the  carving. 

Forecastle  Head.  — The  top,  between  the  rails,  forward  of  fore- 
castle head,  is  plated  over  and  attached  at  the  sides  by  an  angle  bar 
worked  on  the  underside,  or  the  plating  is  flanged  down  on  to  the  side 
plating.  The  forecastle  head  is  connected  to  the  top  plating  by  an 
angle  bar  fitted  on  the  topside  with  packing  iron  in  the  feather  edge. 
Setting  off  the  Draught  Marks  on  the  Stem  and  Stern. — 
Fig.  105  shows  the  outline  of  a  vessel  on  the  stocks.  The  bottom  of  the 
keel  should  be  a  straight  line.     It  is  tested  by  placing  "  dark-sight " 


i 


a 

r 


H 
Z 
0 
a: 


^ 


CO 

o 


49 

be 

o 


UJ 

O 

I 

to 


10 

o 


bo 


CD 


MISCELLANEOUS. 


Ill 


boards,  like  H  in  Fig.  106,  with  an  open  space  P  of  about  ^  of  an  inch, 
on  a  level  with  the  bottom  of  the  keel  at  various  positions  in  the 
length  of  the  vessel,  A,  B,  0 ;  and  adjusting  A  and  C  until  the  sight 
holes  are  in  a  line  with  B  and  each  other,  and  so  that  the  sight  edge 
embraces  the  extreme  bottom  points  of  the  keel.  The  sight  line  may 
then  be  produced  on  to  D— any  upright  at  the  stem — and  a  temporary 
shore  placed  in  for  the  purpose  will  secure  L  in  the  same  way.  To 
these  points  L  and  D  a  straight  edge  J  is  attached.  Then  stand  the 
measuring  batten  G-,  as  shown,  on  top  of  this,  keeping  it  square  to  the 


Fig.    105   {enlarged'). 


Fig.  106 


edge  L  D  with  set  square  K,  and  line  off  the  foot  marks  on  the  stem 
to  about  3  feet  above  the  load-line.  It  is  not  necessary  to  place  any 
figures,  except  in  shallow  draught  boats,  below  about  4  feet,  as  the 
ship  is  never  likely  to  draw  less  water.  The  after  end  may  be  lined 
off  in  the  same  manner  by  producing  C  B  A  to  E  and  placing  straight 
edge  to  points  E  A.  Measure  up  F  from  A  E  the  draught  marks,  and 
stencil  the  figures  in ;  after  which  the  driller  should  cut  them  in  with 
a  chisel,  used  expressly  for  that  purpose.  The  figures  are  G  inches 
deep,  and  are  set  off  as  on  the  batten  G. 


MISCELLANEOUS.  113 

To  Form  an  Oval  Manhole.— In  Fig.   107,  let  A  B  be  the 

longest  dimension.  Bisect  it  in  E,  and  erect  perpendicular  of 
indefinite  length  each  side  of  A  B.  Set  off  E  C  and  E  D  each  equal 
to  half  the  shortest  dimension.  Draw  A  G  and  B  CI1  parallel  and 
equal  to  E  0.  Bisect  A  G  in  F  and  B  G1  in  F1.  Join  F  and  F1  to 
C.  Bisect  E  A  and  E  B  in  M  and  M1  and  join  G  to  M  and  produce 
to  L,  G1  to  M1  and  produce  to  L,  cutting  C  F  and  C  F1  at  H  and  H1. 
Then  bisect  C  H  and  C  H1  in  K  and  K1.  From  K  and  E1  drop 
perpendiculars  cutting  centre  line  C  L,  and  from  the  cutting  point 
draw  arc  H  C  H1.  Then  from  M  and  M1  as  centres  draw  arcs 
H2  A  H  and  H3  B  H1  to  meet  H  C  H1.  Complete  the  opposite  side  in 
the  same  manner. 

Another  Method. — In  Fig.  108,  draw  A  B  and  C  D,  bisected  by 
A  B  in  the  point  E  and  at  right  angles.  On  a  slip  of  paper  F  mark 
the  length  E1  B1  =  E  B,  and  from  E1  make  E1  C1  to  equal  E  C.  Work 
the  slip  into  any  position  so  that  B1  is  on  C  D,  and  C1  on  A  B,  then 
E1  will  give  on  the  line  B1  C1  produced  a  point  for  the  curve.  It  will 
be  readily  seen  that  any  amount  of  points  may  be  found  for  drawing 
in  the  oval.  They  are  shown  by  lines  across  the  figure.  An  easier 
method  still  is  to  construct  an  instrument,  Fig.  109,  with  grooves  for 
the  movable  arm  C  to  work  in,  with  the  points  B1  and  C1  fixed  by 
thumb  screws,  and  the  point  E1  fixed,  but  having  a  pencil  on  the 
lower  side  for  drawing  in  the  oval. 

Different  sized  ovals  are  drawn,  and  an  iron  template  made  of 
each,  with  a  hand-hold  for  the  use  of  the  yard  in  marking  off. 


J  14  NAVAL  ARCHITECTURE. 


WAR     VESSELS 


CHAPTER  XIII. 

Protective  Deck  in  a  Cruiser :  To  Obtain  the  Form — Fairing-up  the  Form — 
Ordinary  Expansion — More  Correct  Method  of  Expansion  —Mode  of 
Plating  -Model  of  Deck — Bevels  for  Beams.  Belt  Armour  and  Deck  in 
a  Battle  Ship:  General  Description  of  the  Structure— Correction  on 
Loft  Floor  for  Belt  Armour  in  Fairing-up  the  Moulded  Form— Belt  Deck 
— Its  Support  -  Connection — Butts  and  Seams — Belt  Armour  on  Box- 
Framing— Armour  Shelf — Protective  Deck  at  Ends  in  a  Battle  Ship  — 
Finish  of  Belt  Armour  at  the  Ends— Fairing-up  the  Belt  Armour — 
Expansion —Moulds  Required  for  Ordering  Plates.  General  Description 
of  the  Structure  of  Ba/rbettes  or  Redoubts:  Expansion  of  the  Armour  — 
Ordering  the  Armour  -  Moulds  Recpaired — Expansion  ttf  Inner  Thick 
Plates —Circular  Barbette —Revolving  Turret  in  Redoubt.  V. 

The  principle  of  "laying-off ' '  the  moulded  form,  on  the  loft  floor, 
of  this  class  of  vessel  is  the  same  as  in  merchant  ships,  so  that  it 
would  be  useless  to  travel  over  the  ground  again.  While  this  is  the 
case,  there  are  special  features  connected  with  the  armour,  shell 
plating,  double  bottoms,  gun  galleries,  moulds,  and  other  considerations 
in  composite  and  sheathed  vessels,  which  do  not  enter  into  iron  or 
steel  merchant  vessels  ;  and,  therefore,  need  some  explanation  here. 
It  is  proposed  to  devote  a  few  chapters  to  these  principal  points. 

ARMOUR. 

Protective  or  Armour  Deck. — Almost  all  war  vessels,  where 
side  armour  is  not  fitted,  have  a  protective  or  armour  deck  extending 
the  entire  length,  or  at  least  over  the  machinery  space,  formed  of  two 
or  three  layers  of  thick  plates.  It  is  placed  about  the  load-line.  In 
some  cases  it  is  of  such  a  simple  character  that  it  needs  no 
explanation,  except  that  given  for  ordinary  decks  on  page  34  ;  but 
where  the  modified  turtle  back  form  is  adopted  the  following  method 
may  be  found  useful. 

To  Obtain  the  Form  of  the  Protective  Deck.— In  the  Body 
plan,  Fig.  no,  arrange  on  the  midship  section  the  distance  below  the 
load-line,  and  from  this  point  A  the  angle  of  the  deck  to  the  ship's 
side  A  T.     The  centre  height  T   U,  above  the  load-line,  should  be 


PROTECTIVE  0 

LOA 


70^ 


80 


PROTECTIVE  1 


I  N  N  E 


PROTECTIVE  PI 


LOA 


FIG.    110. 

BOD'S    |  PLAN 


PROTECTIVE 0 


AFTER 


SO 


I  N  N  El 


ARMOUR.  115 

sufficiently  high  to  get  machinery  comfortably  into  position.  Level 
this  point  U  out  into  each  Body  until  it  cuts  the  produced  side  line 
A  T,  and  reduce  the  knuckle  T  by  a  small  curve,  or  radius.  Place  in 
the  Sheer  Fig.  1 1 1  the  deck  at  the  centre  U,  which  is  generally  main- 
tained for  the  length  of  the  machinery  space.  In  some  cases  it  is 
dropped  sharply  abaft  and  forward  of  machinery  bulkheads,  to  get 
'tween  deck  height  for  the  crew  space,  where  it  is  made  almost  flat, 
with  a  short  curve  down  to  meet  the  side  line.  Some  have  it  con- 
siderably heightened  amidships  to  suit  engines,  etc.  In  Fig.  m,  it  is 
drawn  a  fair  continuous  curve  to  the  after  and  forward  extremities. 
At  the  side  it  is  kept,  as  near  as  possible,  the  same  distance  below  the 
load-line  over  the  machinery  and  magazine  spaces,  and  then  gradually 
faired  in  to  the  end  points.  At  the  after  end  it  covers  the  rudder 
head,  etc.,  while  at  the  fore  end  it  is  attached  to  a  spur  springing 
from  the  ram  (see  Fig.  1 12).  After  these  initial  lines  are  arranged  in 
the  Sheer,  the  centre  heights  and  the  side,  relative  to  the  load-line, 
are  lifted  on  the  frame  stations  and  transferred  into  the  Body.  Level 
lines  are  drawn  through  the  centre  points  towards  the  sides,  and  the 
side  lines  produced  at  about  the  midship  angle,  or  parallel  to  A  T  to 
meet  the  knuckle,  reduced  by  a  small  curve.  At  the  extreme  ends  it 
takes  an  ordinary  camber  form.  In  this  way  the  form,  on  a  few 
sections,  is  approximated.  It  is  necessary,  to  prevent  twist  on  the 
plates,  that  the  sections  be  made  parallel  to  A  T. 

Fairing=up  the  Form  of  the  Protective  Deck. — This 
may  be  done  on  the  buttocks,  but  it  is  best  to  use  diagonal  lines 
like  D  E  and  F  G.  The  cutting  points  of  the  trial  form  are  lifted 
from  the  level  line  A  H,  and  faired  in  the  Sheer  on  the  contracted 
method.  After  a  few  sections  are  faired,  the  intermediates  can  be 
easily  run  in  by  obtaining  spots  on  the  diagonals  and  heights  for  the 
centre  from  the  Sheer,  Fig.  m. 

Expansion  of  the  Protective  Deck.— Assuming  that  the  deck 
is  a  continuous  fair  surface,  the  general  method  is  to  girth  the  centre 
line  U1  Y1  in  Fig.  113 — the  Sheer  enlarged  for  the  fore  end— for  the 
position  of  the  frame  stations,  stern,  and  stem  terminations.  Set  these 
along  a  straight  line  representing  the  centre  line  of  the  vessel,  and 
erect  perpendiculars  from  the  points,  which  are  the  expanded  frame 
stations.  On  these  lay  off  the  girthed  width,  on  corresponding 
sections,  of  the  deck  from  the  centre  line  :  a  curve  through  the  spots 
will  give  J  ¥  X  Y  in  Fig.  114.  Repeat  the  process  for  the  other  side 
of  the  vessel.     Upon  this  expansion  all  the  openings,  longitudinal 


ARMOUR.  115 

sufficiently  high  to  get  machinery  comfortably  into  position.  Level 
this  point  U  out  into  each  Body  until  it  cuts  the  produced  side  line 
A  T,  and  reduce  the  knuckle  T  by  a  small  curve,  or  radius.  Place  in 
the  Sheer  Fig.  m  the  deck  at  the  centre  U,  which  is  generally  main- 
tained for  the  length  of  the  machinery  space.  In  some  cases  it  is 
dropped  sharply  abaft  and  forward  of  machinery  bulkheads,  to  get 
'tween  deck  height  for  the  crew  space,  where  it  is  made  almost  flat, 
with  a  short  curve  down  to  meet  the  side  line.  Some  have  it  con- 
siderably heightened  amidships  to  suit  engines,  etc.  In  Fig.  1 1 1 ,  it  is 
drawn  a  fair  continuous  curve  to  the  after  and  forward  extremities. 
At  the  side  it  is  kept,  as  near  as  possible,  the  same  distance  below  the 
load-line  over  the  machinery  and  magazine  spaces,  and  then  gradually 
faired  in  to  the  end  points.  At  the  after  end  it  covers  the  rudder 
head,  etc.,  while  at  the  fore  end  it  is  attached  to  a  spur  springing 
from  the  ram  (see  Fig.  112).  After  these  initial  lines  are  arranged  in 
the  Sheer,  the  centre  heights  and  the  side,  relative  to  the  load-line, 
are  lifted  on  the  frame  stations  and  transferred  into  the  Body.  Level 
lines  are  drawn  through  the  centre  points  towards  the  sides,  and  the 
side  lines  produced  at  about  the  midship  angle,  or  parallel  to  A  T  to 
meet  the  knuckle,  reduced  by  a  small  curve.  At  the  extreme  ends  it 
takes  an  ordinary  camber  form.  In  this  way  the  form,  on  a  few 
sections,  is  approximated.  It  is  necessary,  to  prevent  twist  on  the 
plates,  that  the  sections  be  made  parallel  to  A  T. 

Fairing=up  the  Form  of  the  Protective  Deck. — This 
may  be  done  on  the  buttocks,  but  it  is  best  to  use  diagonal  lines 
like  D  E  and  F  G.  The  cutting  points  of  the  trial  form  are  lifted 
from  the  level  line  A  H,  and  faired  in  the  Sheer  on  the  contracted 
method.  After  a  few  sections  are  faired,  the  intermediates  can  be 
easily  run  in  by  obtaining  spots  on  the  diagonals  and  heights  for  the 
centre  from  the  Sheer,  Fig.  m. 

Expansion  of  the  Protective  Deck.— Assuming  that  the  deck 
is  a  continuous  fair  surface,  the  general  method  is  to  girth  the  centre 
line  U1  Y1  in  Fig.  113 — the  Sheer  enlarged  for  the  fore  end— for  the 
position  of  the  frame  stations,  stern,  and  stem  terminations.  Set  these 
along  a  straight  line  representing  the  centre  line  of  the  vessel,  and 
erect  perpendiculars  from  the  points,  which  are  the  expanded  frame 
stations.  On  these  lay  off  the  girthed  width,  on  corresponding 
sections,  of  the  deck  from  the  centre  line  ;  a  curve  through  the  spots 
will  give  J  W  X  Y  in  Fig.  1 14.  Repeat  the  process  for  the  other  side 
of  the  vessel.     Upon  this  expansion  all  the  openings,   longitudinal 


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WARD     SHEER. 

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FIG.    114. 

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FIG.    117. 


ARMOUR.  1 1 7 

•J 

and  transverse  bulkheads,  are  indicated  before  arranging  the  plate 
edges ;  which  are  made  parallel  to  the  centre  line  over  the  horizontal 
portion,  and  about  parallel  to  the  ship's  side  on  the  slope.  The 
edges  must  be  straight  between  the  butts.  It  will  be  evident  that 
some  allowance  in  ordering  the  plates  should  be  made,  outside  of  that 
for  planing,  owing  to  the  expansion  being  made  to  the  under  side  of 
the  thick  plating.  The  beams,  and  whatever  comes  in  contact  with 
the  deck,  are  drawn  in  position.  Those  on  the  under  side  in  blue  ink, 
and  those  on  the  top  side  in  red. 

A  More  Correct  Method  of  Protective  Deck  Expansion. — 
Draw  in  the  Body,  Fig.  no,  a  C  and  A  B  square  to  A  T.  Produce 
lines  of  each  section  to  A  B,  shown  dotted.  Lift  from  C  on  C  a  the 
position  of  g,f,  e,  d,  c,  b,  and  a,  and  lay  them  off  from  the  centre  of 
the  expansion  on  the  ordinary  spacing  of  the  frames,  a1,  i1,  c\  d1,  e1,  / l, 
g\  and  C1.  Then  girth  the  midship  form  in  the  Body  from  U  to  T, 
and  T  to  A.  This  laid  out  parallel  from  the  centre  line  of  Fig.  114 
will  give  J  K.  The  correct  position  of  the  stations,  on  this  line,  will 
be  got  by  girthing  L  C1,  and  laying  them  out  along  J  K  from  J,  and 
from  the  points  erect  perpendiculars.  Now  girth  each  section,  in  the 
Body,  from  A  B  to  the  side  line  A  S,  and  the  knuckle  point  T  S,  and 
set  off  these  girths  below  J  K  on  their  corresponding  frames,  which 
will  give  JWMN,  the  expanded  edge  of  the  deck  at  side  ;  and  the 
knuckle  edge  0  P  N.  Next  expand  the  deck  centre,  as  before  explained, 
for  the  true  position  of  the  stations,  and  place  the  points  forward  of 
67  on  the  expansion  centre,  and  erect  perpendiculars;  on  which  plot 
off  the  girthed  widths  of  each  section,  from  the  centre  to  the  knuckle 
line  T  S,  and  you  get  line  0  R  Z,  from  which  it  is  seen  that  the  surface, 
when  properly  developed,  parts  at  the  ends  in  way  of  the  knuckle.  It 
will  be  found  that  if  M  N  P  is  traced  neatly  with  the  position  of  the 
frames,  it  will  fit  into  R,  Z,  only  the  line  of  the  frame  stations  will 
appear  curved. 

This  method  is  adopted,  on  the  loft  floor,  to  secure  the  true  shape 
of  the  deck  at  the  side,  so  that  templates  may  be  made  for  the  platers. 
At  the  extreme  ends,  surface  templates  should  be  taken  from  the  ship. 

Fig.  114  shows  only  the  fore  end  expanded ;  it  is  almost  needless 
to  say  that  the  after  end  is  done  in  the  same  manner. 

Method  of  Plating  the  Protective  Deck.— This  deck  is  plated 
as  described  in  Figs.  114,  115,  and  116.  The  thickest  plating  is  on 
the  slopes,  terminating  at  the  knuckle.  The  top  plate  is  occasionally 
stopped  short  of  the  ship's  side  about  15  inches,  to  allow  for  attaching 
the  upper  frame  knees. 


ARMOUR.  117 

if 

and  transverse  bulkheads,  are  indicated  before  arranging  the  plate 
edges ;  which  are  made  parallel  to  the  centre  line  over  the  horizontal 
portion,  and  about  parallel  to  the  ship's  side  on  the  slope.  The 
edges  must  be  straight  between  the  butts.  It  will  be  evident  that 
some  allowance  in  ordering  the  plates  should  be  made,  outside  of  that 
for  planing,  owing  to  the  expansion  being  made  to  the  under  side  of 
the  thick  plating.  The  beams,  and  whatever  comes  in  contact  with 
the  deck,  are  drawn  in  position.  Those  on  the  under  side  in  blue  ink, 
and  those  on  the  top  side  in  red. 

A  More  Correct  Method  of  Protective  Deck  Expansion. — 
Draw  in  the  Body,  Fig.  no,  a  C  and  A  B  square  to  A  T.  Produce 
lines  of  each  section  to  A  B,  shown  dotted.  Lift  from  C  onCfl  the 
position  of  g,f,  e,  d,  c,  b,  and  a,  and  lay  them  off  from  the  centre  of 
the  expansion  on  the  ordinary  spacing  of  the  frames,  a1,  bl,  c1,  dl,  e1,/1, 
g\  and  C1.  Then  girth  the  midship  form  in  the  Body  from  U  to  T, 
and  T  to  A.  This  laid  out  parallel  from  the  centre  line  of  Fig.  114 
will  give  J  K.  The  correct  position  of  the  stations,  on  this  line,  will 
be  got  by  girthing  L  C1,  and  laying  them  out  along  J  K  from  J,  and 
from  the  points  erect  perpendiculars.  Now  girth  each  section,  in  the 
Body,  from  A  B  to  the  side  line  A  S,  and  the  knuckle  point  T  S,  and 
set  off  these  girths  below  J  K  on  their  corresponding  frames,  which 
will  give  J  W  M  N,  the  expanded  edge  of  the  deck  at  side  ;  and  the 
knuckle  edge  0  P  N.  Next  expand  the  deck  centre,  as  before  explained, 
for  the  true  position  of  the  stations,  and  place  the  points  forward  of 
67  on  the  expansion  centre,  and  erect  perpendiculars;  on  which  plot 
off  the  girthed  widths  of  each  section,  from  the  centre  to  the  knuckle 
line  T  S,  and  you  get  line  0  R  Z,  from  which  it  is  seen  that  the  surface, 
when  properly  developed,  parts  at  the  ends  in  way  of  the  knuckle.  It 
will  be  found  that  if  M  N  P  is  traced  neatly  with  the  position  of  the 
frames,  it  will  fit  into  R  Z,  only  the  line  of  the  frame  stations  will 
appear  curved. 

This  method  is  adopted,  on  the  loft  floor,  to  secure  the  true  shape 
of  the  deck  at  the  side,  so  that  templates  may  be  made  for  the  platers. 
At  the  extreme  ends,  surface  templates  should  be  taken  from  the  ship. 

Fig.  114  shows  only  the  fore  end  expanded;  it  is  almost  needless 
to  say  that  the  after  end  is  done  in  the  same  manner. 

Method  of  Plating  the  Protective  Deck.— This  deck  is  plated 
as  described  in  Figs.  114,  115,  and  116.  The  thickest  plating  is  on 
the  slopes,  terminating  at  the  knuckle.  The  top  plate  is  occasionally 
stopped  short  of  the  ship's  side  about  15  inches,  to  allow  for  attaching 
the  upper  frame  knees. 


118 


NAVAL  ARCHITECTURE. 


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\1_7    ^—J  '  VU 


The  method  of  forming  the  edges  is  seen  in  Fig.  116,  and  of  the 

butts  in  Fig.  115;   only  the  bottom  thickness  is  attached  to  the  beams. 

The  fore  and  aft  edges  are  straight  between  the  butts,  as  shown  in  the 

pi       n5>  expansion,    Fig.    114. 

The  Figs.  1 12  and  1 17 
explain  the  method  of 
finishing  on  the  stem. 
The  after  end  is  secured 
to  the  stern  plating  by 
an  angle  bar.  This  deck 
being  continuous,  all 
bulkheads  are  cut  and  connected  to  the  deck  by  single  bars.  Owing 
to  the  numerous  longitudinal  bulkheads  in  the  machinery  space, 
which  give  support  to  the  deck,  only  occasional  strong  beams  are 
fitted  there. 

Model  of  the  Protective  Deck, — The  most  correct  way  to 
arrange  and  order  the  plating  is  to  make  a  wood  block  model,  on  a 
\  inch  scale,  of  the  deck  from  or  about  the  level  plane  A  H  in  Fig.  no. 
This  is  rubbed  smooth  and  painted  white.      The  beams,  bulkheads, 

Fig.    116. 


openings,  etc.,  are  marked  upon  it,  and  then  the  edges  and  butts  of 
the  plating  are  arranged.  There  should  be  no  difficulty  in  ordering 
the  plates  from  this  model.  At  the  irregular  parts  the  correct  surface 
of  any  plate  may  be  got  by  tracing  it,  and  then  laying  the  tracing 
flat.     Order  the  plate  in  the  usual  way  described  on  page  50. 

Beams  Supporting  the  Protective  Deck. — When  this  deck 
has  much  curve  fore  and  aft,  the   beam  flange  is  bevelled  to  suit. 


ARMOUR. 


119 


The  bevels  are  lifted  in  the  same  manner  as  already  described  for  the 
frames  of  merchant  vessels. 

Belt  Armour  and  Deck  in  a  Battle  Ship.— After  the  moulded 

form  of  the  ship  is  faired -up  on  the  loft  floor,  the  position  of  the 


Fig.  118. 


Fig.    126. 


armour  belt  relative  to  the  load-line  is  marked  on  the  midship  section, 
as  shown  in  the  enlarged  sketch  in  Fig.  118,  and  also  on  the  Body 
sections,  Fig.  1 1 9.     The  armour  will  project  out  beyond  the  moulded 


Fig.   120. 

FORE    AND    AFT    SECTIONAL    ELEVATION    OF 

END    ARMOUR. 


LIQHT    DECK 


BELT  DECK 


ARMOUR.  121 

form  the  thickness  of  the  adjacent  shell  plates,  which  are  inside 
strakes,  so  that  the  extreme  side  will  be  flush  for  some  distance.  In 
fairing-up,  on  the  loft  floor,  in  the  first  case  the  moulded  form,  this 
projection  is  deducted ;  therefore,  it  must  be  added  on  in  drawing  in 
the  armour.  The  armour  belt  extends  at  least  over  the  length  of  the 
machinery  space,  magazines,  and  shell  rooms.  It  is  crowned  by  a 
level  belt-deck,  formed  of  two  thicknesses  of  steel  plating,  reaching 
over  the  length  of  the  armour,  being  connected  at  the  sides  and  ends 
as  shown  in  Figs.  118  and  120,  and  supported  by  strong  bulb  angle 
beams  attached  to  alternate  frames.  The  butts  and  seams  of  the 
plating  are  made  the  same  as  in  Figs.  1 15  and  1 16.  The  side  armour, 
which  is  not  connected  at  the  butts,  is  fixed  against  teak,  or  other 
hard  wood,  backing  about  5  inches  thick :  which  is  supported  by  one 
or  two  thick  continuous  longitudinal  steel  plates  riveted  to  the  frame 
work  as  shown  in  Fig.  118.  The  entire  system  is  called  "Box 
framing."  It  is  made  level  on  the  top  and  parallel  to  the  ship's  side. 
The  frames  next  to  the  backing  are  double,  as  shown  in  the  plan, 
Fig.  123.  The  deck  or  shelf,  G  H  in  Fig.  118,  on  which  the  armour 
rests,  is  inclined  inboard  to  about  3  to  5  degrees  from  the  side  line  G, 
which  is  vertically  parallel  to  the  top  G1.  The  lower  edge  of  the 
armour  is  made  to  suit  the  bevel  of  this  shelf.  The  section  is  the 
same  thickness,  in  most  cases,  for  about  half  its  depth  and  tapered 
from  that  point,  as  shown  in  Fig.  118.  At  the  extreme  fore  and  aft 
ends  it  is  slightly  reduced  in  thickness.  To  begin  the  laying-off,  the 
form  of  the  armour  with  the  frame  work  is  drawn  in  at  each  section 
in  the  Body,  Fig.  119,  and  faired-up  on  the  floor  by  level  or  diagonal 
lines  in  the  usual  way.  Where  there  is  much  fore  and  aft  curve  on 
the  level  lines,  the  thickness  of  the  armour  should  be  set  in  square  to 
these  outside  lines  in  Fig.  124,  and  curves  traced  through  the  spots 
will  give  correct  points,  on  the  sections,  for  the  inside  edge. 

When  the  armour  belt  only  extends  over  the  midship  portion,  as 
in  Fig.  129,  an  armoured  deck,  called  protective  deck,  is  arranged 
forward  and  abaft  of  the  belt,  and  run  to  suitable  heights  at  the 
extreme  ends  ;  at  the  aft  end  to  cover  the  steering  gear,  and  at  the 
fore  end  to  give  strength  in  ramming.  This  deck  is  a  continuation 
of  the  armour  shelf,  but  cambered  up  at  the  centre  for  greater 
efficiency.  The  armour,  with  the  framework,  is  carried  across  the 
ship  at  the  ends  of  the  belt  to  form  protection  against  fore  and  aft 
fire.  It  rests  upon  the  protective  deck  extended,  as  shown  in  Fig. 
120  and  cross  section  Fig.  121,  supported  by  beams  and  a   strong 


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RMOUR   BELT 


Fig.   123. 
LONGITUDINAL  SECTIONAL  PLAN   OF     ARMOUR   BELT 


T  SIOE    ARMOUR 


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Fig.  125. 
EXPANSION    OF    ARMOUR 


ARMOUR.  123 

bulkhead  with  large  brackets.  The  butts  and  edges  of  the  armour 
are  not  caulked.  The  finish  of  the  lower  edge  is  shown  by  the  Fig. 
127,  and  of  the  top  by  Fig-.  126. 

The  Fig.  120  is  a  fore  and  aft  sectional  elevation  through  the  end 
armour,  and  Fig.  121  a  cross  section  at  30  frame,  showing  how  the 
belt  and  protective  decks  are  finished  and  the  armour  supported.  In 
Fig.  122  is  shown,  in  plan,  the  method  of  terminating  the  side  and 
end  armour  with  a  watertight  shoe.  Fig.  123  is  a  longitudinal 
sectional  plan  showing  the  disposition  of  the  armour  butts  and  box 
framing. 

Fairingsaip  the  Belt  or  Side  Armour.  — This  may  be  done 
by  close  level  lines,  or  straight  diagonals,  in  the  usual  way.  It  is  laid 
out  in  the  Figs.  119  and  124,  faired  by  six  curved  diagonals.  No.  4 
is  first  placed  in  the  Body  square  to  each  frame  curve,  and  the  others 
are  at  an  equal  girthed  distance  each  side  of  it.  Then,  taking  the  side 
line  A  B  in  Fig.  119  as  a  base,  lift  from  it  on  the  run  of  the  diagonals 
the  position  of  the  frames,  and  set  them  off  on  their  respective  stations 
in  the  Fig.  124,  and  fair  lines  in.  If  the  moulded  form  of  the  ship  is 
fair,  these  ought  to  be  correct.  The  inside  of  the  armour  and  frame 
work  may  be  faired  in  the  same  way,  by  setting  in  square  to  these 
lines  the  thickness  of  armour,  and  passing  curves  through  the  spots, 
which  should  be  transferred  on  each  frame  and  diagonal  into  the  Body, 
aud  curves  put  through  the  points. 

Expansion  of  the  Belt  Armour.  — Girth  on  67  frame  in  the 
Body,  Fig.  119,  the  distance  apart  of  the  diagonals.  Draw  in  Fig.  125 
a  straight  and  parallel  line  to  the  base  of  the  Fig.  124,  and  set  off 
the  position  of  the  curved  diagonals  to  it,  which  should  be  parallel 
distances  apart.  Then  girth  each  diagonal  in  the  Fig.  124  for  the 
position  of  the  frame  stations,  and  lay  them  off  on  their  respective  sides 
of  the  midship  frame  67,  of  Fig.  125,  and  on  their  corresponding 
diagonals.  A  curve  passed  through  these  points  will  give  shape  of  the 
frames  in  the  expansion.  The  form  of  the  lower  edge  may  be  found 
by  girthing  its  position  on  each  section,  in  the  Body,  Fig.  119, 
relative  to  No.  1  diagonal,  and  setting  the  distances  off  below  D  1  on 
their  frames  in  the  expansion.  A  line  drawn  through  the  spots  will 
give  lower  edge  0  D  of  the  armour.  Do  the  same  with  the  top  edge 
relative  to  D  6  and  you  get  E  F.  It  is  necessary  to  find  the  form  and 
position  of  the  butts  for  ordering  the  plates,  which  you  can  do  with 
relation  to  the  frames,  or  they  may  be  squared  down  on  to  the  curved 
diagonals  in  the  Fig.  124,  and  then  girthed  on  each  side  and  trans- 


ARMOUR.  123 

bulkhead  with  large  brackets.  The  butts  and  edges  of  the  armour 
are  not  caulked.  The  finish  of  the  lower  edge  is  shown  by  the  Fig. 
127,  and  of  the  top  by  Fig.  126. 

The  Fig.  120  is  a  fore  and  aft  sectional  elevation  through  the  end 
armour,  and  Fig.  121  a  cross  section  at  SO  frame,  showing  how  the 
belt  and  protective  decks  are  finished  and  the  armour  supported.  In 
Fig.  122  is  shown,  in  plan,  the  method  of  terminating  the  side  and 
end  armour  with  a  watertight  shoe.  Fig.  123  is  a  longitudinal 
sectional  plan  showing  the  disposition  of  the  armour  butts  and  box 
framing. 

Fairingtfiip  the  Belt  or  Side  Armour.— This  may  be  done 
by  close  level  lines,  or  straight  diagonals,  in  the  usual  way.  It  is  laid 
out  in  the  Figs.  119  and  124,  faired  by  six  curved  diagonals.  No.  4 
is  first  placed  in  the  Body  square  to  each  frame  curve,  and  the  others 
are  at  an  equal  girthed  distance  each  side  of  it.  Then,  taking  the  side 
line  A  B  in  Fig.  119  as  a  base,  lift  from  it  on  the  run  of  the  diagonals 
the  position  of  the  frames,  and  set  them  off  on  their  respective  stations 
in  the  Fig.  124,  and  fair  lines  in.  If  the  moulded  form  of  the  ship  is 
fair,  these  ought  to  be  correct.  The  inside  of  the  armour  and  frame 
work  may  be  faired  in  the  same  way,  by  setting  in  square  to  these 
lines  the  thickness  of  arrnour,  and  passing  curves  through  the  spots, 
which  should  be  transferred  on  each  frame  and  diagonal  into  the  Body, 
and  curves  put  through  the  points. 

Expansion  of  the  Belt  Armour.  — Girth  on  67  frame  in  the 
Body,  Fig.  119,  the  distance  apart  of  the  diagonals.  Draw  in  Fig.  125 
a  straight  and  parallel  line  to  the  base  of  the  Fig.  124,  and  set  off 
the  position  of  the  curved  diagonals  to  it,  which  should  be  parallel 
distances  apart.  Then  girth  each  diagonal  in  the  Fig.  124  for  the 
position  of  the  frame  stations,  and  lay  them  off  on  their  respective  sides 
of  the  midship  frame  67,  of  Fig.  125,  and  on  their  corresponding 
diagonals.  A  curve  passed  through  these  points  will  give  shape  of  the 
frames  in  the  expansion.  The  form  of  the  lower  edge  may  be  found 
by  girthing  its  position  on  each  section,  in  the  Body,  Fig.  119, 
relative  to  No.  1  diagonal,  and  setting  the  distances  off  below  D  1  on 
their  frames  in  the  expansion.  A  line  drawn  through  the  spots  will 
give  lower  edge  C  D  of  the  armour.  Do  the  same  with  the  top  edge 
relative  to  D  6  and  you  get  E  F.  It  is  necessary  to  find  the  form  and 
position  of  the  butts  for  ordering  the  plates,  which  you  can  do  with 
relation  to  the  frames,  or  they  may  be  squared  down  on  to  the  curved 
diagonals  in  the  Fig.  124,  and  then  girthed  on  each  side  and  trans- 


124  NAVAL  ARCHITECTURE. 

ferret!  into  the  expansion.     The  form  of  the  end  armour  may  be  got 
by  drawing  out  cross  sections,  like  Fig.  121. 

Moulds  for  Ordering  the  Belt  Armour. —  A  surface  mould 
is  made  from  the  expansion  of  each  plate,  showing  the  position  of  the 
frames  and  bolts  for  attaching  the  armour,  together  with  moulds  for 
the  top,  bottom,  ends,  and  two  vertical  winding  sight  moulds  for 
fixing  on  to  the  outside  edge  of  the  plate  near  each  butt.  Altogether 
seven  moulds  are  required  for  each  plate.  The  butts  are  vertical  and 
square  to  the  outside  surface  on  the  top  edge. 

Barbette. — Fig.  128  shows  the  sectional  plan  and  elevation  of  a 
forward  barbette,  standing  on  the  belt  deck,  from  which  a  big  twin 
gun  is  worked.  Its  position  is  further  seen  in  Fig.  129.  The  armour 
is  supported  by  teak  backing  against  one  or  two  thick  steel  plates, 
riveted  to  the  frame  work — these  plates  take  the  armour  bolts.  The 
inner  edge  A  B  C  is  parallel  to  the  outside  of  the  armour  D  E  F. 
The  crown  G  H  is  level  with  the  belt  deck,  and  made  of  thick  steel 
plates,  which  at  the  sides  lie  at  an  inclination  of  about  5  degrees  to 
suit  gun  depression.  An  opening  is  arranged  in  the  crown  to  allow 
for  the  training  of  the  gun.  The  armour  butts  are  made  square  to 
the  outside  surface  to  come  on  to  the  frames.  The  butts  of  the  inner 
thick  plates  also  come  on  frames.  The  seam  edges  are  formed  by 
lapping  each  thickness,  as  in  Fig.  130A.  Intercostal  plates  a,  b,  r,  d, 
e,  and /are  fitted  in  between  the  frames,  clear  of  the  bolts,  for  support. 
The  armour  is  slightly  reduced  in  thickness  at  the  after  end  from  P  P1, 
and  a  joint  K1  L1  arranged  clear  of  the  intercostals.  Below  K1  L1  the 
armour  is  considerably  reduced  in  thickness.  The  forward  end  of  the 
barbette  is  circular  with  the  roller  path,  and  the  after  end  is  circular 
with  a  suitable  radius,  while  in  between  is  a  straight  line  The  inside 
surface  of  the  thin  armour  may  be  made  flush  with  the  top  thickness, 
which  gives  parallel  backing. 

Expansion  of  the  Barbette  Armour. — To  draw  an  approxi- 
mate expansion,  show  in  the  line  R  S  T  in  the  plan  at  half  the  thick- 
ness of  the  armour,  and  produce  the  direction  of  the  frames  to  cut 
this  line,  then  girth  from  R  to  T,  marking  on  the  lath,  or  paper,  the 
position  of  the  frames,  butts,  and  centre  line.  Lay  this  girth  R  T,  with 
frame  positions,  on  a  base  R1  T1,  Fig.  130,  and  erect  frame  lines.  Set 
off  G1  H1  parallel  to  R1  T1,  and  at  a  distance  equal  to  the  depth  of  the 
armour  ;  also  K  L  equal  in  position  to  K1  L1.  Arrange  the  butts  of 
the  armour,  and  the  thick  plates  on  the  frames,  to  clear  each  other  : 
and  the  edges  of  the  thick  plates  to  clear  the  intercostals  and  armour 


Fig.    128. 

FORE     &    AFT     SECTIONAL     ELEVATION 


Q  CROWN        PLATE 


BELT        DECK 


PLAN 


w> 


Fig.    129. 

BATTLE     SHIP. 


SHEER 

SPAR DECK 


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126  NAVAL  ARCHITECTURE. 

bolts.  This  plan,  which  shows  one  side  of  the  barbette,  is  suitable 
for  yard  purposes,  or  may  be  used  for  obtaining  an  approximate 
account  of  the  weight  of  the  armour. 

Ordering  the  Barbette  Armour. — The  barbette  is  mocked  up, 
built  in  skeleton  fashion,  on  the  loft  floor  and  wood  moulds  made 
therefrom.  One  for  each  end  of  every  plate,  and  flat  moulds  for  the 
bottom  and  top,  and  one  for  the  outside  surface,  with  two  vertical 
sight  winding  pieces  for  the  outside  to  get  the  round  plates  into 
form.  The  inner  plating  may  ah:o  be  measured  from  the  loft  at  the 
same  time,  due  allowance  being  made  for  planing  edges  and  butts,  or 
a  correct  account  of  the  armour  for  ordering  may  be  got  by  expanding 
on  the  left  floor  the  outside  surface  D  E  F,  and  supplying  the  moulds 
before-mentioned.  A  correct  account  of  the  inner  thick  plates  may  be 
got  by  expanding  the  surface  between  the  plates  in  the  usual  manner. 

Circular  Barbette. — They  are  sometimes  arranged  in  complete 
circular  form,  as  in  Fig.  131,  with  a  supply  armoured  tube  from 
magizines,  etc.,  placed  in  the  centre  of  the  roller  path  B  B.  An 
a  -count  of  this  barbette  armour  is  easily  found  by  laying  the  plan 
form  down  on  the  loft  floor,  and  producing  the  direction  of  the  frame 
stations  to  the  outside  surface  line.  Girth  this  line  for  the  stations, 
and  lay  them  out  on  a  base,  and  erect  station  perpendiculars.  Show 
in  the  depth,  which  will  be  parallel  to  the  base.  This  may  be  got  by 
producing  the  top  and  side  lines  in  the  section  until  they  meet.  This 
surface  expansion  is  sufficient,  with  the  ends,  top,  bottom,  surface, 
and  sight  moulds  of  each  plate,  for  ordering  the  armour.  The  butts 
are  on  the  frames  as  before  explained. 

Revolving  Armoured  Turret  or  Redoubt. — An  armoured 
revolving  turret  carrying  guns  is  occasionally  fitted  inside  of  a 
barbette  of  the  form  of  Fig.  130  or  Fig.  131.  In  Fig.  132  is  given 
an  outline  sketch  showing  such,  which  needs  no  further  explanation. 
The  armour,  framing,  etc.,  being  arranged  and  expanded  in  the  same 
way  as  the  barbette  previously  mentioned. 


ENLARGED 
SIDE    SECTION 


ELT  DECK 


Fig.  131. 
FORE    AND    AFT    SECTIONAL    ELEVATION. 


ENLARGED 
SIDE     SECTION 


1 


FORE    END 


PLAN 


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THIN     PLATING 


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ABOUT     £4"    APART 


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Fig.   132. 

FORE    &    AFT    SECTIONAL    ELEVATION 
REVOLVING     TURRET     IN     FORWARD     BARBETTE. 


CROWN      Plat, 


DRWARD. 


AR  _DECK 


rjjj^o* 


L!BRA«y* 


tjisn^ 


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DRWARD. 


Fig.   133. 
BODY    SECTIONS    OF    A    BATTLE    SHIP. 


AFTER. 


FORWARD. 


_3PAR       Dtci, 


SHELL  PLATING  AND  BILGE  KEELS.  12', 


CHAPTER  XIV. 

Outer  Bottom  Plate  Edges  of  a  Battle  Ship — Outer  Bottom  Plate  Edges  of  a 
Cruiser  Bilge  Keels  ;  where  best  Placed — Bossed  Frames  Forward  in 
way  of  the  Ram. 


SHELL  PLATING  AND  BILGE  KEELS. 

Outer  Bottom  Plate  Edges  of  a  Battle  Ship.— These  are 
first  arranged,  approximately,  on  the  Body  sections  as  in  Fig.  133,  in 
conjunction  with  the  inner  bottom  longitudinal  sight  edges  ;  and 
afterwards  lined  off  and  faired  on  the  model. 

In  Fig.  133,  show  in  the  extent  and  position  of  the  side  armour 
and  deck  lines.  Set  off  around  the  midship  section  of  each  Body  the 
sight  edges  of  the  shell  plates,  which  are  made  of  a  suitable  width 
somewhere  about  50  inches,  or  they  are  lifted  from  the  "scantling 
section."  The  fiat  plate  keel  is  an  outside  strake,  divided  equally 
each  side  of  the  centre  line,  with  a  doubling  or  double  plate  keel 
inside.  The  strakes  next  to  the  top  and  bottom  of  the  armour  belt 
should  be  inside  and  flush  with  it.  Next  draw  in  the  position  of  the 
screw  boss,  the  flats  at  the  extreme  ends,  and,  it  is  best  to  approximate, 
the  lines  for  the  inner  bottom  longitudinals  as  explained  on  page  130, 
so  that  the  shell  edges  may  be  kept  clear — they  are  indicated  by 
dotted  lines.  The  edges  of  the  shell  plating,  above  the  armour  belt, 
are  sheered  to  the  upper  deck  line,  with  a  slight  taper  towards  the 
ends.  Those  below  the  belt  are  straight  to  the  stem  and  stern,  with 
considerable  taper,  and  made  to  clear  inner  bottom  longitudinals. 
"  Stealers "  are  introduced  to  prevent  narrow  strakes.  Under  the 
extreme  bottom  a  slight  round  is  given  to  form  a  better  line.  The  plate 
keel  is  of  parallel  girth  for  the  best  part  of  the  vessel's  length,  and 
lifted  up  at  the  ends  to  take  away  the  appearance  of  drooping.  The 
parts  before  and  abaft  of  the  belt  are  divided  in  suitably  ;  the  upper 
edge  of  the  strake  below  the  armour  may  be  stepped  up  to  make  a 
more  pleasing  line  and  division,  and  to  get  it  clear  of  the  protective 
deck  side.  Care  should  be  taken  at  the  screw  boss  to  arrange  the 
edges  for  one  furnaced  plate,  or  to  make  a  plate  edge  on  the  centre  of 
the  round,  and  have  two  furnace  plates  as  shown  in  Fig.  134. 

Edges  should  clear  all  watertight  flats.  After  arrangement  in  the 
Body,  they  are  lifted  and  faired  on  the  model  in  the  manner  described 


^£st    LIBRAE 


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ft*&* 


SHELL  PLATING  AND  BILGE  KEELS.  12^ 


CHAPTER  XIV. 

Outer  Bottom  Plate  Edges  of  a  Battle  Ship— Oiiter  Bottom  Plate  Edges  of  a 
Cruiser  Bilge  Keels  ;  where  best  Placed — Bossed  Frames  Forward  in 
way  of  the  Ram. 


SHELL  PLATING  AND  BILGE  KEELS. 

Outer  Bottom  Plate  Edges  of  a  Battle  Ship.— These  are 
first  arranged,  approximately,  on  the  Body  sections  as  in  Fig.  133,  in 
conjunction  with  the  inner  bottom  longitudinal  sight  edges  ;  and 
afterwards  lined  off  and  faired  on  the  model. 

In  Fig.  133,  show  in  the  extent  and  position  of  the  side  armour 
and  deck  lines.  Set  off  around  the  midship  section  of  each  Body  the 
sight  edges  of  the  shell  plates,  which  are  made  of  a  suitable  width 
somewhere  about  50  inches,  or  they  are  lifted  from  the  "scantling 
section."  The  flat  plate  keel  is  an  outside  strake,  divided  equally 
each  side  of  the  centre  line,  with  a  doubling  or  double  plate  keel 
inside.  The  strakes  next  to  the  top  and  bottom  of  the  armour  belt 
should  be  inside  and  flush  with  it.  Next  draw  in  the  position  of  the 
screw  boss,  the  flats  at  the  extreme  ends,  and,  it  is  best  to  approximate, 
the  lines  for  the  inner  bottom  longitudinals  as  explained  on  page  130, 
so  that  the  shell  edges  may  be  kept  clear — they  are  indicated  by 
dotted  lines.  The  edges  of  the  shell  plating,  above  the  armour  belt, 
are  sheered  to  the  upper  deck  line,  with  a  slight  taper  towards  the 
ends.  Those  below  the  belt  are  straight  to  the  stem  and  stern,  with 
considerable  taper,  and  made  to  clear  inner  bottom  longitudinals. 
"  Stealers "  are  introduced  to  prevent  narrow  strakes.  Under  the 
extreme  bottom  a  slight  round  is  given  to  form  a  better  line.  The  plate 
keel  is  of  parallel  girth  for  the  best  part  of  the  vessel's  length,  and 
lifted  up  at  the  ends  to  take  away  the  appearance  of  drooping.  The 
parts  before  and  abaft  of  the  belt  are  divided  in  suitably  ;  the  upper 
edge  of  the  strake  below  the  armour  may  be  stepped  up  to  make  a 
more  pleasing  line  and  division,  and  to  get  it  clear  of  the  protective 
deck  side.  Care  should  be  taken  at  the  screw  boss  to  arrange  the 
edges  for  one  furnaced  plate,  or  to  make  a  plate  edge  on  the  centre  of 
the  round,  and  have  two  furnace  plates  as  shown  in  Fig.  134. 

Edges  should  clear  all  watertight  flats.  After  arrangement  in  the 
Body,  they  are  lifted  and  faired  on  the  model  in  the  manner  described 


128 


NAVAL  ARCHITECTURE. 


on  page  45,  any  correction  necessary  being  transferred  back  into  the 
Body.  They  are  further  faired-np  on  the  loft  floor  before  scrieving 
down  (see  page  48).  The  butts  and  thicknesses  of  the  plating  are 
set  off  on  a  J  inch  scale  "expansion  plan"  explained  on  page  48, 
and  made  to  clear  the  butts  of  the  armour,  deck  stringers,  and 
longitudinals.  They  are  afterwards  transferred  on  to  the  model  and 
adjusted  if  necessary. 

Outer  Bottom  Plate  Edges  of  a  Cruiser.  -These  are  arranged 
on  the  Body  (Fig.  134)  in  a  similar  manner  to  a  merchant  ship,  set 
forth  on  page  45.  The  flat  keel  plate  is  an  outside  strake  and  of 
parallel  girth  for  almost  the  full  extent,  only  at  the  extreme  ends  it  is 
lifted  up  to  form  a  better  line.  Before  arranging  plate  edges,  the 
position  of  the  decks,  longitudinals,  and  screw-boss  should  be 
indicated  on  the  Body.     The  strakes  above  the  protective  deck  are 

Fig.    135. 


1  •  > 

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73 


79 


85 


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103 


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sheered  to  the  upper  deck  line,  and  tapered  slightly  towards  the  ends  ; 
the  taper  being  greatest  upon  those  strakes  nearest  to  the  protective 
deck.  The  upper  deck  sheer  strake  stands  about  9  inches  above  the 
deck  line,  slightly  increasing  towards  the  ends.  The  lower  strakes, 
except  the  keel  plate  and  garboards,  are  drawn  in  straight  from  the 
midship  section  to  the  stem  and  stern,  about  square  to  the  frame 
curves,  to  divide  the  space  to  the  best  advantage.  Owing  to  the 
fineness  of  the  ship's  form,  it  is  necessary  to  introduce  several 
"  stealers  "  or  "  lost  strakes  "  to  prevent  narrow  plating.  When  all 
the  lines  are  drawn  fair  in  the  Body,  their  position  is  girthed  on  each 
section  on  narrow  strips  of  paper  and  transferred  on  to  the  model,  and 
faired  in  the  usual  way.     They  are  also  tried  on  the  loft  floor  before 


scrieving  in. 


Bilge  Keels  are  placed  on  the  turn  of  each  bilge,  being  the 
points  of  least  resistance  to  the  vessel's  speed  and  that  of  greatest 


RUISER. 


OUT 


Fig.    134. 
BODY    SECTIONS    OF    AN    UNARMOURED    CRUISER. 


FORWARD 


SHELL  PLATING  AND  BILGE  KEELS.  129 

efficiency  against  rolling.  The  line  is  shown  in  each  Body,  in  Figs. 
133  and  134,  drawn  as  square  as  possible  to  frame  curves  throughout 
its  length  ;  which  is  about  half  length  amidships.  This  line  appears 
curved  when  placed  in  the  Sheer  and  Half  Breadth. 

Bossed  Frames  Forward. —  It  may  be  as  well  to  note  here,  that 
sometimes  the  fore  end  frames  are  bossed  for  some  distance  from  the 
stem,  in  a  line  with  the  centre  of  the  ram.  Particular  attention 
should  be  given  to  the  line  through  the  centre  of  the  boss,  to  make  it 
graceful  and  easy.  Such  a  line  is  shown  in  Fig.  135.  The  manner 
of  obtaining  and  fairing  is  on  the  method  explained  on  page  12,  when 
the  initial  centre  line  is  settled. 


10 


SHELL  PLATING  AND  BILGE  KEELS.  129 

efficiency  against  rolling.  The  line  is  shown  in  each  Body,  in  Figs. 
133  and  134,  drawn  as  square  as  possible  to  frame  curves  throughout 
its  length  ;  which  is  about  half  length  amidships.  This  line  appears 
curved  when  placed  in  the  Sheer  and  Half  Breadth. 

Bossed  Frames  Forward. —  It  may  be  as  well  to  note  here,  tbat 
sometimes  the  fore  end  frames  are  bossed  for  some  distance  from  the 
stem,  in  a  line  with  the  centre  of  the  ram.  Particular  attention 
should  be  given  to  the  line  through  the  centre  of  the  boss,  to  make  it 
graceful  and  easy.  Such  a  line  is  shown  in  Fig.  135.  The  manner 
of  obtaining  and  fairing  is  on  the  method  explained  on  page  12,  when 
the  initial  centre  line  is  settled. 


10 


130  NAVAL  ARCHITECTURE. 


CHAPTER  XV. 

To  Obtain  and  Fair  the  Lines  of  the  Inner  Bottom  of  a  Cruiser— Expansion  of 
the  Inner  Bottom  — Expansion  of  the  Longitudinals— Expansion  of  a 
Longitudinal  on  Curved  Diagonals  — Mockiiig-up  System  of  Expansion— 
To  Obtain  and  Fair-up  the  Inner  Bottom  Lines  of  a  Battle  Ship—  Expan- 
sion of  the  Inner  Bottom — Bevels  on  Inner  Bottom  Frames. 


DOUBLE  BOTTOMS. 

It  is,  almost,  an  invariable  rule  to  fit  war  vessels  with  a  double 
bottom  on  the  cellular  system  for  at  least  the  length  of  the  machinery 
space,  with  ordinary  framing  at  the  ends. 

To  Obtain  and  Fair  the  Lines  of  the  Inner  Bottom  of  a 
Cruiser. — After,  or  at  the  same  time  as,  the  shell  plating  sight  edges 
are  settled,  the  curve  of  the  inner  bottom,  ABO  and  A  B1  C1,  on  the 
midship  section,  is  transferred  from  the  "  scantling  section  "  on  to  the 
large  sized  Body  sections  (Fig.  136),  usually  \  an  inch  =  to  1  foot. 
These  sections  are  got  out,  at  convenient  distances  apart,  for  the  full 
extent  of  the  double  bottom.  Sufficient  allowance  is  made  on  B  C 
and  B1  C1  to  get  the  frame  bar  through,  and  the  watertight  collar 
fitted  comfortably  round  it.  The  shell  edge,  01  C3  and  0  and  C2,  is  lun 
in,  either  in  the  Sheer  or  on  the  model,  clear  of  the  outer  bottom 
edges,  if  possible,  and  the  line  faired-up  and  corrected  in  the  Body. 
The  intersection  of  this  line  with  each  frame  will  be  the  point  of  the 
inner  bottom  termination  at  the  sides.  Draw  level  lines  through  each 
point  like  B  C  and  B1  C1,  about  the  midship  width,  and  fair  the  inner 
edge  in  the  Half  Breadth.  The  heights  of  the  inner  bottom  fore  and 
aft  on  the  centre  line  are  usually  fixed  on  the  "  keelson  plan,1'  and 
lifted  therefrom  at  each  section,  and  set  above  the  base  on  the  centre 
line  of  the  Body.  The  sight  edges  of  the  longitudinals,  E  D  F  and 
0  M  N,  should  now  be  drawn  in  clear  of  the  plate  edges,  as  far  as 
possible,  and  placed  about  the  middle  of  a  shell  strake.  They  are  faired 
in  the  Half  Breadth  by  lifting  the  cutting  points  from  the  Body  square 
to  the  centre,  and  transferring  (see  F  D  E  in  Fig.  137 ).  Then,  from  the 
cutting  points  of  F  D  E,  in  Fig.  136,  draw  in  the  longitudinal  square 
to  each  frame  and  about  the  midship  width,  or  of  a  graduated  specified 
taper  ;  and  through  these  points,  in  conjunction  with  the  centre  heights 
and  the  knuckle,  approximate  curves  of  the  inner  bottom  may  be 


RD 


Fig.  136. 

SECTIONS 


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132  NAVAL  ARCHITECTURE. 

drawn.  Other  longitudinal  girders  may  now  he  shown  in  the  same 
manner.  You  are  now  in  a  position  to  test  the  fairness  of  the  inner 
hottoin,  which  will,  undoubtedly,  require  some  modification.  Sections 
33,  C>3,  and  93  should  be  considered  fixed  points,  and  the  intermediates 
faired,  which  may  be  done  on  the  buttocks  by  lifting  the  points,  s,  t,  w, 
■i\  //,  etc.,  on  P  R  and  P'R1,  from  the  base  and  transferring  the  heights 
into  Fig.  137,  or  diagonals  square  to  the  curves  may  be  used.  It  is 
usual  to  do  this  on  the  contracted  method. 

The  top  edge  of  the  longitudinal,  H  (I  L,  is  faired  by  lifting  the 
distances  square  out  from  the  centre,  and  transferring  them  into  the 
Half  Breadth.  They  should  require  little  or  no  alteration,  seeing  the 
longitudinals  are  square  to  the  frames.  It  will  be  evident  that  the 
intermediate  inner  bottom  points  for  the  scrieve  board  are  lifted  from 
these  faired  lines.  Another  method,  differing  slightly,  is  explained  on 
page  135. 

Expansion  of  the  Inner  Bottom  in  a  Cruiser. — After  the 
fairing  of  the  sections  is  completed,  bend  laths,  or  strips  of  drawing- 
paper,  round  the  lines  of  the  inner  bottom  curves  in  Fig.  136,  and 
mark  on  them  the  position  of  the  centre,  longitudinals,  knuckle,  and 
the  shell  point.  On  a  base,  representing  the  length  of  the  double 
bottom  on  the  same  scale,  erect  the  frame  stations,  and  set  off  on 
their  corresponding  frames  the  girthed  distances,  and  fair  curves 
through  the  spots,  which  will  give  you  the  expanded  form.  Then 
girth  the  position  of  the  edges  of  the  innner  bottom  plating  from  the 
"  scantling  section,"  or  fix  them  suitably  to  clear  longitudinals,  and 
lay  them  off  from  the  expansion  centre  to  the  same  scale  ;  producing 
lines  through  the  points,  parallel  to  the  centre.  Care  should  be  taken 
to  avoid  at  the  ends  feather-edged  plates,  and  also  to  keep  the  edges 
clear  of  the  watertight  longitudinals.  It  is  best  where  overlapping 
cannot  be  avoided  to  adopt  the  step  system,  or  introduce  "  stealers.''' 
The  position  of  the  shell  butts,  manholes,  engine  and  boiler  seating, 
longitudinal  and  transverse  bulkheads,  watertight  divisions,  tunnels, 
openings,  and  whatever  has  to  come  in  contact  with  the  plating,  is 
distinctly  marked  in  coloured  ink  ;  then,  the  butts  are  arranged  clear 
of  those  of  the  shell  and  longitudinals  ;  and  the  plates  ordered.  Owing 
to  the  round  fore  and  aft,  a  little  should  be  allowed  on  the  length  of 
the  plates,  or  the  correct  position  of  the  frames  can  be  found  in  the 
first  case  by  expanding  longitudinally. 

Expansion  of  the  Longitudinals  in  a  Cruiser. — In  Fig.  138, 
draw  down  straight  line  a1  a,  representing  the  length  of  the  tank  on 


DOUBLE  BOTTOMS.  133 

the  same  scale  as  the  Body  sections  :  and  mark  off  the  position  of  the 
sections,  from  which  points  erect  perpendiculars.  In  Fig.  136  make 
a  p  and  a1  p1  of  equal  length,  and  at  equal  distances,  and  parallel  to 
D  G  and  D  G  respectively  on  each  side,  a  a1  being  parallel  to  the  base 
line.  From  points  a1,  p1,  a,  and  p,  erect  perpendiculars,  and  produce 
the  line  of  the  longitudinals  at  each  frame  to  meet  these  in  the  points 
/,  k,  h,  [/,/,  and  so  on,  shown  by  dotted  lines.  In  expansion  (Fig.  138) 
set  off  a1  f  a  and  p1  f1  p  parallel,  and  distance  a  p  apart,  taken  from 
Fig.  136.  Then  lift  from  a  and  a1  the  points  b,  c,  d,  e,f,g,  h,  i,  Jc,  I, 
and  set  them  on  their  respective  frames  above  a  a1,  in  Fig.  138; 
through  which  draw  curve  A.  Lift  from  p  and  p1  the  points  b1,  e\ 
d1,  etc.,  and  lay  them  off  on  their  respective  frames  below  p1  p,  in 
Fig.  138,  and  draw  B.  Girth  A  with  a  batten  for  the  position  of 
the  frames,  and  place  the  batten  on  a1  a,  keeping  63  fair  with  63, 
and  mark  expanded  position  of  the  frames.  Girth  B  likewise,  and 
lay  off  the  points  around  63  frame  on  p1  p.  Join  the  top  and 
bottom  spots,  shown  by  dotted  lines.  From  a  fa1,  in  Fig.  136,  lift 
the  position  of  the  line  F  D  E  and  L  G  H,  on  the  run  of  the  longitudi- 
nal, and  mark  them  off  on  the  expanded  frame  stations,  in  Fig.  138, 
from  a1  a,  which  will  give  lines  C  and  D.  This  is  approximately  the 
expanded  form  of  the  longitudinal.  If  the  lines  D  G,  E  H,  and  the 
intermediates,  were  parallel  to  each  other,  this  would  be  a  correct 
development.  The  method  just  described  is  found  sufficiently  correct 
for  the  midship  body,  where  the  lines  of  the  longitudinal  at  each 
section  are  about  parallel  to  one  another.  When  they  are  not  quite 
parallel,  which  is  an  evidence  of  twist,  if  the  expansion  is  taken  in 
short  lengths  to  embrace  only  one  plate,  there  is  not  much  error 
involved.  At  the  extreme  ends  the  lines  are  usually  considerably  out 
of  the  parallel,  indicating  great  twist  on  the  plate ;  in  such  a  case  the 
mocking-up  system  explained  further  on  is  adopted. 

Expansion  of  a  Longitudinal  by  Curved  Diagonals. — In 
Fig-  !39»  the  Body,  A  G  is  the  sight  edge  and  a  <j  the  inner  edge  of 
the  longitudinal.  Produce  lines  A  a,  B  b,  C  c,  etc.,  indefinitely  in 
each  direction.  Fix  a  point  a1  for  curved  diagonal  a1  if,  and  make  it 
square  to  each  section  in  the  points  a1,  b1,  c1,  etc.  From  A  and  It  draw 
A  L  and  h  k  parallel  to  a1  g\  by  setting  off  a1  h  to  the  right  of  the 
points  a1,  b1,  c\  and  a1  A  to  the  left,  on  the  run  of  the  longitudinal 
sections.  Number  these  diagonals  1,  2,  and  3.  Girth  each  from  the 
base  A  h  for  the  points  a1,  b1,  c\  etc.,  and  lay  them  off  on  their  corre- 
sponding stations  in  the  Fig.  140,   through  which  draw  fair  lines. 


134 


NAVAL  ARCHITECTURE. 


Make  L1  A1,  in  Fig.  141,  parallel  to  H  K.  Set  off  g2a2  and  h1  ¥  equal 
in  distance  to  A  a1  and  a1  h  respectively  in  the  Body,  and  parallel  to 
L1  A1.  Girth  each  diagonal  from  G7  frame  in  the  Fig.  140  for  the 
frame  stations,  and  lay  them  out  on  their  corresponding  lines  from 
No.  07  in  the  expansion  Fig.  141— No.  1  diagonal  on  A1  L1,  No.  2  on 
a2  g2,  No.  3  on  hl  l;\  Draw  vertical  curves  through  the  spots,  which 
will  give  form  of  the  frames.  Upon  these  indicate  the  position  of 
the  sight  edge  A  G,  relative  to  a1  //  in  the  Body,  i.e.,  lift  a1  A,  bl  B, 
r1  0,  il1  1),  e1  E,  p  F,  <f  G.  Set  off  a1  A,  ¥  B,  c1  C,  (P  D  on  their 
respective  frames,  G7,  55,  49,  43,  below  a2  f,  and  e1  E,,/'1  F,  (f  G, 


Fig.    142. 


BODY. 


LEVEL    lIaII 


above  ci~  if  on  corresponding  frames  37,  31,  25.  A  curve  through  the 
spots  will  give  longitudinal  sight  edge  A1  G1.  In  the  same  manner 
lay  off  a  g  relative  to  a'  //'.  The  points  a,  b,  c  will  be  below,  and  d,  e, 
f,g  above  <r  ;f.  Then  the  lines  as  g*  and  A1  G1,  Fig.  141,  show  the 
expansion  of  the  surface  of  the  longitudinal  A  G  g  a. 

All  the  frames  and  butts  are  now  shown  across,  and  the  plates 
ordered.  The  method  comes  very  near  to  accuracy,  if  carefully 
carried  out.  Only  the  after  end  is  shown,  but  it  will  be  evident 
that  the  fore  end  can  be  done  in  the  same  way. 


35 

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Fig.   141. 

EXPANSION 


DOUBLE  BOTTOMS. 


135 


Expansion  by  the  Mocking=up  System. — Fig.  142  shows 
part  of  the  Body  plan  on  the  loft  floor  with  longitudinal  sight  edge 
and  the  intersection  form  at  various  stations.  Drop  perpendiculars 
from  the  points  A,  B,  C,  D,  etc.,  and  from  a,  b,  c,  d,  etc.,  on  to  a 
convenient  level  line  L  M.  Transfer  the  sight  edge  A  G  into  the 
Half  Breadth,  lifting  the  cutting  points  square  out  from  the  centre 
line.  Then  make  skeleton  templates  at  each  section  showing  the 
form,  like  H  E  e  J.  Erect  these  in  the  Half  Breadth  on  their 
respective  stations  with  the  edge  of  the  mould,  A,  B,  C,  D,  E,  F,  and 
G,  fair  to  the  sight  edge  just  transferred  from  the  Body.  Secure 
them,  perpendicular,  by  a  light  cross  piece  tacked  at  the  bottom  to 
the  floor,  and  attach  them  to  each  other  by  a  fore  and  aft  piece,  P. 
The  top  outside  edges  of  these  templates  give  the  correct  form  of  the 
longitudinal  surface  and  the  position  of  the  frames.  A  mould,  like 
Fig.  143,  is  then  made  for  each  plate  showing  the  extreme  edges, 

Fig.    143. 


with  cross  pieces  for  the  position  of  the  frames,  and  end  pieces  for 
the  butt  straps.  The  latter  should  be  arranged  for  the  strap  to  clear 
the  vertical  bars.  This  is  the  method  generally  adopted  where  there 
is  considerable  twist,  and  absolute  correctness  is  required.  '1  he 
watertight  longitudinal  butts  are  usually  treble  riveted  and  the  non- 
watertight  double. 


Note.  —  It  may  be  noted  that  an  easy  way  of  transferring  a  line  from  the 
loft  floor  on  to  a  board  for  making  a  template  is  to  place  small  flat-headed  nails 
with  the  edge  of  the  head  resting  on  the  line,  and  then  lay  a  board  on  the 
top,  and  a  little  pressure  will  cause  them  to  adhere  to  the  board,  when  it  may 
be  lifted  and  the  curve  drawn  in  pencil  through  the  points. 


134 

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DOUBLE  BOTTOMS. 


135 


Expansion  by  the  Mocking=up  System.— Fig.  142  shows 
part  of  the  Body  plan  on  the  loft  floor  with  longitudinal  sight  edo-e 
and  the  intersection  form  at  various  stations.  Drop  perpendiculars 
from  the  points  A,  B,  C,  D,  etc.,  and  from  a,  b,  c,  d,  etc.,  on  to  a 
convenient  level  line  LM.  Transfer  the  sight  edge  AG  into  the 
Half  Breadth,  lifting  the  cutting  points  square  out  from  the  centre 
line.  Then  make  skeleton  templates  at  each  section  showing  the 
form,  like  HEeJ.  Erect  these  in  the  Half  Breadth  on  their 
respective  stations  with  the  edge  of  the  mould,  A,  B,  C,  D,  E,  F,  and 
G,  fair  to  the  sight  edge  just  transferred  from  the  Body.  Secure 
them,  perpendicular,  by  a  light  cross  piece  tacked  at  the  bottom  to 
the  floor,  and  attach  them  to  each  other  by  a  fore  and  aft  piece,  P. 
The  top  outside  edges  of  these  templates  give  the  correct  form  of  the 
longitudinal  surface  and  the  position  of  the  frames.  A  mould,  like 
Fig-  143.  is  then  made  for  each  plate  showing  the  extreme  edges, 

Fig.    143. 


with  cross  pieces  for  the  position  of  the  frames,  and  end  pieces  for 
the  butt  straps.  The  latter  should  be  arranged  for  the  strap  to  clear 
the  vertical  bars.  This  is  the  method  generally  adopted  where  there 
is  considerable  twist,  and  absolute  correctness  is  required.  '1  he 
watertight  longitudinal  butts  are  usually  treble  riveted  and  the  non- 
watertight  double. 


Note. -It  may  be  noted  that  an  easy  way  of  transferring  a  line  from  the 
loft  floor  on  to  a  board  for  making  a  template  is  to  place  small  flat-headed  nails 
with  the  edge  of  the  head  resting  on  the  line,  and  then  lay  a  board  on  the 
top,  and  a  little  pressure  will  cause  them  to  adhere  to  the  board,  when  it  may 
be  lifted  and  the  curve  drawn  in  pencil  through  the  points. 


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DOUBLE  BOTTOMS.  1 37 

To  Obtain  and  Fair = up  the  Inner  Bottom  Lines  of  a 
Battle  Ship. — The  inner  bottom  is  different  in  that  it  extends  to 
the  armour  shelf  on  each  side.  The  form  is  first  approximated  on 
the  Body  sections  (Fig.  144)  in  the  following  manner.  When  the  ship 
has  a  raised  keel,  lift  from  the  "  keelson  plan "  the  height  of  the 
centre  keelson  above  the  base  line,  at  each  section,  for  the  length  of 
the  double  bottom,  and  set  the  distances  up  the  centre  of  the  Body 
above  the  corresponding  base.  The  moulded  midship  depth  will  be 
from  3(i  to  40  inches,  and  it  may,  or  may  not,  be  parallel  to  the  keel 
fore  and  aft.  Where  the  ship  is  on  a  level  keel,  with  a  parallel 
keelson,  the  top  will  be  represented  by  one  point  as  in  the  Fig.  144. 
The  central  part  of  the  inner  bottom  is  made  level  fore  and  aft  at 
each  side  of  the  centre  line,  to  take  the  width  of  the  keelson  top  bars. 
The  midship  form  may  now  be  drawn  in  by  setting  off  the  breadth 
A  B  in  the  Fig.  147,  and  transferring  it  into  the  Body  A1  B1.  Then 
the  curve  is  lifted  from  Fig.  147,  the  "scantling  section,"  on  the 
longitudinals  to  their  specified  moulded  width,  or  it  may  be  got  by  a 
gradual  taper  of  about  4  to  6  inches  from  the  centre  point  E  to  the 
top  point  F,  and  brought  out  to  B1  with  an  easy  continuous  curve. 
The  midship  is  duplicated  in  both  bodies.  The  end  sections  27 
and  94  are  next  settled  in  the  same  way,  only  the  taper  may  be 
slightly  more  towards  the  top.  Care  being  exercised  not  to  take  too 
much  out  of  the  floors  for  manholes,  and  yet  to  have  easy  access 
to  all  parts  of  the  bottom.  Diagonal  lines  C  D  and  O1  D1  are 
drawn  in  each  Body ;  and  the  outer  bottom  form,  on  this  line,  lifted 
on  each  section  from  C  and  C1,  and  the  poiuts  set  off  on  the 
"  contracted  principle,"  as  to  the  ship's  length,  above  a  base,  from 
which  the  line  a,  b,  r,  in  Fig.  145,  is  drawn.  The  moulded  depth 
of  the  double  bottom  on  the  run  of  the  diagonal  C  D  and  C1  D1  is 
lifted  from  the  sections,  a1  d  on  27  frame,  bl  e  on  67,  and  &  f  on  9J-, 
and  transferred  into  the  Fig.  145,  a1  d  set  above  a  =  a  d\  bl  e  above 
b  =  b  e1,  c1/  above  c  =  c  f1.  A  batten  is  pinned  to  these  points 
d1,  e\  f1,  and  the  inner  bottom  drawn  a  gradual  and  fair  taper  to  the 
out  bottom  a,  b,  c.  The  distances,  on  each  frame  section,  lifted  and 
transferred  into  the  Body  on  the  diagonal,  or  diagonals,  will  give 
spots  on  the  intermediate  frames,  and  in  conjunction  with  E  and 
A1  B1,  which  is  the  same  for  all  sections,  will  enable  the  approximate 
form  on  each  section  to  be  traced  in.  These  lines  are  then  faired  up 
by  a  few  additional  diagonals  and  buttocks  in  the  same  manner  as 
C  D.     The  upper  part  may  be  faired  by  a  close  level  line  or  two. 


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DOUBLE  BOTTOMS.  139 

The  longitudinals  are  then  drawn  square  to  the  frames  for  the 
depth  of  the  double  bottom.  It  is  usual  to  test  the  fairness,  in  the 
Half  Breadth,  of  the  top  edge  of  the  longitudinals  in  the  same  way  as 
described  for  the  outer  bottom  edges. 

Expansion  of  the  Inner  Bottom  of  a  Battle  Ship. — An 
expansion  of  the  inner  bottom  surface  is  made  on  a  I  -inch  scale  for 
ordering  the  plates,  and  for  the  guidance  of  the  workmen  in  plating 
same. 

The  plating  is  carried  to,  or  just  beyond,  the  wing  passage  bulk- 
head to  h,  in  Fig-.  147.  Girth  the  inner  bottom,  in  Fig-.  144,  on  each 
section  from  the  centre  line  for  the  point  h,  and  the  position  of  the 
fore  and  aft  bulkheads,  longitudinals,  and  midship  section  plate  edges. 
Lay  these  distances  off  in  the  expansion  (Fig.  146)  from  the  base  or 
centre  line.  Run  blue  dotted  lines  through  the  points  of  the  longi- 
tudinals and  athwartship  tank  divisions,  full  blue  lines  showing  fore 
and  aft  bulkheads,  athwartship  bulkheads,  engine  and  boiler  seating 
girders,  shaft  passages,  and  whatever  will  come  in  contact  with  the 
top  of  the  inner  bottom.  Then  the  plate  sight  edges  may  be  drawn 
in  black  ink  parallel  to  the  ship's  centre,  as  far  as  they  will  go  without 
crossing  watertight  longitudinal  divisions.  It  may  be  necessary  at 
the  ends  to  step  them  back,  or  introduce  stealers.  The  manholes  for 
entrance  to  the  inner  bottom  are  also  arranged  to  clear  and  in  suitable 
positions.  The  butts  of  the  outer  bottom  plating  and  longitudinals 
are  indicated  in  red,  and  the  butts  of  the  inner  bottom  are  lined  off, 
and  the  plates  ordered  from  this  plan.  A  little  allowance  should  be 
made  in  the  length  of  the  plates  for  the  curve  on  the  bottom  fore  and 
aft,  or  the  fore  and  aft  expanded  form  found. 

Bevels  on  Inner  Bottom  Frames.— Where  the  double  bottom 
has  fore  and  aft  curve  bevels  must  be  lifted  in  the  usual  way,  com- 
mencing from  the  protective  deck,  and  given  on  boards  to  the  frame 
turners  to  bevel  the  frames. 


Fig.    147. 
BATTLES  H  I  P. 

MIDSHIP      SECTION 


SPAR      DECK 


LOAQ   LINE 


GUN  GALLERIES  OR  SPONSORS.  141 


CHAPTER  XYI. 

Obtaining  and  Fairing  Lines  of  a  Midship  Gun  Gallery — Expansion— Obtaining 
and  Fairing  Lines  of  a  Midship  Gun  Gallery  of  Conical  Type— Expansion 
of  Conical  Type— Semi  Egg-shaped  Forward  Gun  Embrasure — Another 
Form  of  End  Gun  Gallery — Expansion  of  End  Gallery. 


GUN  GALLERIES  OR  SPONSONS. 

It  is  not  easy,  nor  necessary,  to  give  all  the  different  forms  of 
galleries  erected  on  the  sides  of  vessels  for  carrying  guns;  for  they  are 
the  outcome  of  the  special  design  of  ship  and  gnu,  which  alters  very 
frequently  :  therefore,  a  few  of  the  most  important  and  generally 
adopted  will  be  described. 

Midship  Gun  Gallery. — It  is  usual  to  draw  the  galleries  to  a 
large  scale,  say  \  inch  equal  to  1  foot.  For  this  purpose,  lift  the 
position  G  from  the  small  design,  and  show  it  in  Fig.  148  with  frames 
60,  61,  etc.  Set  off  A  B  and  A1  B1  parallel  to  and  at  a  convenient 
and  equal  distance  from  the  centre  line  of  the  vessel,  and  draw  in  the 
Body  the  form  of  the  frame  stations  for  the  extent  of  the  fore  and 
aft  spread,  also  the  centre  of  the  gallery,  which  lines  transfer  into  the 
Half  Breadth  on  the  rail,  knuckle,  and  at  suitable  levels.  The  form 
C  D  E,  in  the  plan,  is  settled  to  suit  the  extreme  range  of  the  gun  and 
shield.  Having  fixed  it,  lift  the  line  C  D  E  on  each  frame  from  A  B, 
and  lay  the  points  out  from  A1  B1  in  the  Body  on  the  knuckle  level,  or 
levels— if  there  is  fore  and  aft  sheer.  The  bulwark  between  the  knuckle 
and  rail  is  made  vertical,  as  shown  at  each  section.  Then  draw  in 
D1  H  with  a  suitable  angle  to  the  ship's  side,  and  continue  the  points 
a,  h,  c,  d  parallel  to  D1  H,  to  meet  their  respective  frames ;  projecting 
the  cutting  points  into  the  Sheer  as  shown  by  dotted  lines,  through 
which  draw  the  form  line  L  M  K  on  the  ship's  side.  For  the  purpose 
of  easy  explanation,  the  moulded  form  of  the  ship  is  shown  the  same 
on  both  sides  of  the  gun  centre,  which  may  not  be  the  case.  Now 
square  down  from  the  Sheer  the  cutting  points  of  L  M  K  with  the 
level  lines  on  to  their  corresponding  levels  in  the  Half  Breadth.  Lift 
the  level  line  breadths  from  A1  B1  in  the  Body,  i.e.,  e,f,  (/,  h,  etc.,  and 
transfer  them  on  to  their  respective  frames  in  the  Half  Breadth, 
through  which,  with  terminations  on  the  ship's  side,  draw  fair  form 
of  the  level  lines  1  and  2.    Then  you  have  the  necessary  form— faired. 


142  NAVAL  ARCHITECTURE. 

The  bulwark  part  N  0  P,  necessary  for  the  working  of  the  gun,  may 
be  made  of  hinged  doors,  or  cut  out  altogether  with  a  moulding  on 
the  outside,  and  an  angle  bar  on  the  inside  carried  along  the  edge  for 
stiffening. 

Expansion  of  Midship  Gallery. — It  is  assumed  that  the  ship 
has  no  sheer  in  way  of  this  gallery.  On  page  145  a  method  is 
shown  for  setting  off  the  line  when  there  is  sheer. 

In  the  expansion  make  D2  Ds  equal  to  D1  Df.  Draw  C1  E1  through 
D3  and  parallel  to  C2  Ea,  and  both  at  right  angles  to  D2  D:i.  Girth 
rail  and  knuckle  in  the  Half  Breadth  from  D  to  butt  0  and  E, 
marking  at  the  same  time  the  position  of  the  frames.  Lay  the 
knuckle  girth  off  about  Ds,  and  that  of  the  rail  on  D:i.  Join  top  and 
bottom  points,  and  you  have  expanded  bulwark  plating. 

The  lower  portion,  or  sponson,  is  expanded  by  drawing  in  the  Body 
the  set  line  R  S  square  to  H  D1,  and  R1  R2  in  the  expansion  of  parallel 
distance  D2  81  equal  to  D1  S.  Then  lift  from  R,  in  the  Body,  R  a\ 
R  b\  R  e1,  R  d1,  and  R  S,  and  place  them  on  their  respective  sections 
in  the  expansion,  which  will  give  dotted  line  T  T,  the  form  of  the 
gallery  through  8  R.  Girth  this  line  for  the  position  of  the  frames, 
which  set-off  on  the  set  line  R1  R2  around  S1.  From  these  points 
the  expanded  frames  are  shown  dotted  in  and  numbered.  Then 
measure  the  distance  from  the  set  line  R  S  in  the  Body  to  the 
knuckle  points  a,  b,  c,  a,  and  D1,  and  lay  them  off  on  the  expanded 
frames  above  R1  R2,  through  which  points  a2,  b2,  c2,  etc.,  draw  curve. 
Next  lift  from  the  Body  the  distances,  on  the  run  of  the  section, 
below  the  set  line  R  S  to  frame  cutting  points,  and  measure  off  below 
R^'  in  the  expansion.  Trace  fair  curve  through  the  spots.  This 
gives  the  expanded  lower  edge.  The  figure  R1  X  R2  D2  is  the 
expanded  form.  The  plating  may  be  ordered  in  two  or  three  plates 
with  vertical  butts  ;  allowance  being  made  for  the  knuckle  and  shell 
connection  over  and  above  this  expansion. 

In  the  case  of  a  plate  edge  SW,  shown  in  the  Body,  running  fore 
and  aft.  Lift  the  distance  from  R  S,  on  each  section,  and  set-off  in 
the  expansion  below  R1  R2.  The  termination  may  be  got  by  lifting- 
cutting  point  at  W  square  to  R  S,  and  measuring  it  off  parallel  to 
RXR2  to  cut  line  R\  X,  R2,  by  which  you  get  W1  and  W2.  Draw 
curve  W1  S1  W2  through  points,  and  you  have  the  line  on  the  expansion. 

Midship  Gun  Gallery  of  a  Conical  Type.  In  Fig.  149,  draw 
A  B  and  A1  B1  in  plan  and  cross  section  at  a  suitable,  equal,  and 
parallel  distance  to  the  centre  line  of  the  ship.     Set  off  from  A1  B1  on 


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HALF         BREALpTH 


GVN  GALLERIES  OR  SPONSORS.  143 

L  L  1  the  outstretch  of  the  gallery  sufficient  to  work  gun  to  the  range 
and  depression.  Join  C  to  A1  with  a  suitable  angle.  The  point  C  is 
generally  kept  on  a  level  with  the  lower  edge  of  the  gunwale  moulding. 
Draw  in  the  Body  the  level  lines  L  L  2,  L  L  3,  etc.,  and  produce  them 
into  the  Sheer.  Then,  with  radii  equal  at  each  level  line  of  the  Body, 
to  the  distance  from  the  vertical  A1  B1  to  C  A1,  describe  in  the  Half 
Breadth  from  D  radiating  level  lines,  1,  2,  3,  4,  5,  and  6.  Show  in 
the  Half  Breadth  position  of  the  frame  stations  40,  41,  42,  43,  44, 
and  45.  Lift  the  ordinates  of  these  radiating  lines  from  A  B  at  each 
station,  and  transfer  them  into  the  Body  from  A1  B1  on  their  corre- 
sponding levels.  The  points  of  termination  on  A1  B1  may  be  got  by 
lifting  the  distances  of  the  frame  stations  from  D,  say  D  to  42,  D  to  41 , 
D  to  40,  and  setting  them  off  from  A1  along  A1  E.  Square  up  these 
points  to  A1  C,  and  level  in  the  intersections,  as  shown,  on  to  A1  B1, 
which  will  enable  you  to  draw  the  form  of  the  cross  sections.  The 
side  of  the  vessel  may  now  be  shown  in  the  Body,  if  not  already 
done,  relative  to  A1  B1,  and  the  ordinates  for  the  same  on  the  level 
lines,  rail,  etc.,  transferred  into  the  Half  Breadth,  for  drawing  in  the 
ship's  form  at  the  various  levels.  The  cutting  points  with  the 
radiating  planes  are  then  squared  into  the  Sheer,  indicated  by  dotted 
lines  ;  and  the  frame  stations,  cutting  ship's  side  form  in  the 
Body,  levelled  over  into  the  Sheer  on  to  their  corresponding  frames, 
allow  the  form  line  RTS  on  the  ship's  side  to  be  drawn  in.  The 
bulwark  above  C1  C  is  made  to  take  usual  sheer,  and  in  the  section  is 
vertically  parallel  to  A1  B1,  and  carried  up  to  the  height  of  the  under 
side  of  the  hammock  berthing  or  rail,  being  joined  by  easy  curves  to 
the  ship's  form  before  and  abaft  the  gallery. 

Expansion  of  the  Plating  of  a  Conical  Gallery. — From  A1 
as  centre  describe  arcs  of  circles,  as  shown,  with  radii  equal  to  AV, 
A1  b,  and  so  on.  Then  girth  each  level  line  in  the  Half  Breadth  from 
A  B  for  the  position  of  the  ship's  side,  the  frame  stations,  and  the 
centre.  Measure  the  girths  from  A1  C  around  their  corresponding 
level  lines  in  the  expansion,  a  a1,  b  b1,  c  c1,  etc.,  marking  the  position 
of  the  side,  frames,  and  centre  at  the  same  time,  and  draw  lines  through 
the  spots.  The  figure  F,  G,  H,  K  is  the  form  of  the  developed  plate 
below  the  knuckle  C^C.  Allowance  must  be  made  over  and  above 
this  at  the  edges  for  connection. 

For  the  bulwarks,  or  the  part  above  the  knuckle,  continue  CI  K  to 
M.  Make  K  M  equal  to  C  N,  and  L  K  square  to  K  M,  and  of  length 
equal  to  the  girth  of  M1  L1  in  the  Half  Breadth.    Draw  M  0  parallel  to 


OF  CAUfO*^ 


GUN  GALLERIES  OR  SPONSONS.  143 

L  L  1  the  outstretch  of  the  gallery  sufficient  to  work  gun  to  the  range 
and  depression.  Join  C  to  A1  with  a  suitable  angle.  The  point  C  is 
generally  kept  on  a  level  with  the  lower  edge  of  the  gunwale  moulding. 
Draw  in  the  Body  the  level  lines  L  L  2,  LL 3,  etc.,  and  produce  them 
into  the  Sheer.  Then,  with  radii  equal  at  each  level  line  of  the  Body, 
to  the  distance  from  the  vertical  A1  B1  to  C  A1,  describe  in  the  Half 
Breadth  from  D  radiating  level  lines,  1,  2,  3,  4,  5,  and  6.  Show  in 
the  Half  Breadth  position  of  the  frame  stations  40,  41,  42,  43,  44, 
and  45.  Lift  the  ordinates  of  these  radiating  lines  from  A  B  at  each 
station,  and  transfer  them  into  the  Body  from  A1  B1  on  their  corre- 
sponding levels.  The  points  of  termination  on  A1  B1  may  be  got  by 
lifting  the  distances  of  the  frame  stations  from  D,  say  J)  to  42,  D  to  41 , 
D  to  40,  and  setting  them  off  from  A1  along  A1  E.  Square  up  these 
points  to  A1  C,  and  level  in  the  intersections,  as  shown,  on  to  A1  B1, 
which  will  enable  you  to  draw  the  form  of  the  cross  sections.  The 
side  of  the  vessel  may  now  be  shown  in  the  Body,  if  not  already 
done,  relative  to  A1  B1,  and  the  ordinates  for  the  same  on  the  level 
lines,  rail,  etc.,  transferred  into  the  Half  Breadth,  for  drawing  in  the 
ship's  form  at  the  various  levels.  The  cutting  points  with  the 
radiating  planes  are  then  squared  into  the  Sheer,  indicated  by  clotted 
lines  ;  and  the  frame  stations,  cutting  ship's  side  form  in  the 
Body,  levelled  over  into  the  Sheer  on  to  their  corresponding  frames, 
allow  the  form  line  R  T  S  on  the  ship's  side  to  be  drawn  in.  The 
bulwark  above  C1  C  is  made  to  take  usual  sheer,  and  in  the  section  is 
vertically  parallel  to  A1  B1,  and  carried  up  to  the  height  of  the  under 
side  of  the  hammock  berthing  or  rail,  being  joined  by  easy  curves  to 
the  ship's  form  before  and  abaft  the  gallery. 

Expansion  of  the  Plating  of  a  Conical  Gallery. — From  A1 
as  centre  describe  arcs  of  circles,  as  shown,  with  radii  equal  to  AV, 
A1  b,  and  so  on.  Then  girth  each  level  line  in  the  Half  Breadth  from 
A  B  for  the  position  of  the  ship's  side,  the  frame  stations,  and  the 
centre.  Measure  the  girths  from  A1  C  around  their  corresponding 
level  lines  in  the  expansion,  a  a1,  b  b1,  c  c1,  etc.,  marking  the  position 
of  the  side,  frames,  and  centre  at  the  same  time,  and  draw  lines  through 
the  spots.  The  figure  F,  G,  H,  K  is  the  form  of  the  developed  plate 
below  the  knuckle  010.  Allowance  must  be  made  over  and  above 
this  at  the  edges  for  connection. 

For  the  bulwarks,  or  the  part  above  the  knuckle,  continue  G  K  to 
M.  Make  K  M  equal  to  C  N,  and  L  K  square  to  K  M,  and  of  length 
equal  to  the  girth  of  M1  L1  in  the  Half  Breadth.    Draw  M  0  parallel  to 


144  NAVAL  AECHITECTURB. 

K  L,  unci  girth  M1  O1  for  length  of  M  0.  Connect  0  to  L.  The  other 
side  of  the  figure  is  got  in  the  same  manner.  The  depth  of  L  0  will 
be  more  if  C'N1  is  not  level  with  CN.  In  other  words,  account  must 
be  taken  of  any  sheer  in  E,  S.  For  simplicity  it  is  assumed  that  there 
is  no  sheer  in  this  case.  The  gallery  is  sometimes  made  with  hinged 
doors  from  VW,  but  in  a  number  of  cases  the  bulwarks  are  cut  down 
as  shown  by  dotted  lines,  V1  X  W1  and  W2  X1,  to  allow  for  firing  of  the 
gun  at  extreme  angles.  In  such  a  case  the  rail  moulding  is  carried 
round  V1  X  W1  with  an  angle  bar  on  the  inside  to  stiffen  the  edo-e. 

The  plating  of  the  part  below  the  knuckle  may  be  arranged  with 
a  seam  fore  and  aft  between  A1  and  C,  or  vertical  plates  with  butts  to 
clear  frames  may  be  fitted.  The  sponson  is  stiffened  by  angle  iron 
frames  with  solid  floors  lightened  by  manholes. 

Semi  Egg=shaped  Forward  Gun  Embrasure. — Occasionally, 
it  is  constructed  in  the  following  manner.  In  Fig.  150,  line  in  the 
Body  the  moulded  form  of  the  ship  at  each  frame  in  way  of  the  gun, 
and  place  the  outline  in  the  Sheer  and  Half  Breadth.  Fix  the 
centre  A  B  and  A1  B1,  and  trace  in  the  gun  outline  with  shield  C. 
Describe,  in  section,  the  arc  DEF  to  clear  shield  when  at  depression 
or  elevation.  Lift  the  distance  A1  E,  from  the  Body,  on  level  line  3 
into  the  Half  Breadth  A  E1,  and  sketch  in  approximate  horizontal  form 
F  E1  CI,  such  to  allow  the  working  of  the  gun  when  at  extreme  range. 
Square  up  F1  and  G  into  the  Sheer  on  L  L  3,  and  level  over  from  the 
Body  D  and  F  on  to  96  frame,  by  which  four  points  are  secured,  and 
the  approximate  form  on  the  ship's  side  is  drawn.  Line  off  in  the 
Sheer  and  Body  closely  spaced  level  lines,  and  square  the  cutting  points 
in  the  Sheer  into  the  Half  Breadth  on  to  their  corresponding  level  lines, 
which,  in  conjunction  with  the  distances  of  J,  H,  K,  and  L  lifted 
from  Body  on  to  A  E1,  will  allow  the  approximate  form  of  the  level 
lines  in  the  Half  Breadth  to  be  drawn.  Transfer  this  form  at  each 
section  into  the  Body  :  and  fair -up  in  the  Half  Breadth  on  diagonal 
lines  like  MN  and  MO.  The  form  of  the  embrasure  should  be  so 
arranged  that  the  gun  will  clear  the  plating  in  all  possible  positions. 
A  port  P  R  S  is  made  for  working  the  gun  at  extreme  angles,  which 
means,  that  the  lowrer  edge  sill  should  clear  when  at  a  depression  of 
say  25  degrees,  and  the  top  edge  at  an  elevation  of  30  degrees  at  80 
degrees  range.  Doors  are  fitted  to  this  port,  hinged  fore  and  aft,  or 
towards  the  forecastle  deck.  The  plating,  forming  the  embrasure,  is 
usually  wTorked  in  two,  butted  flush  as  shown,  and  edges  flanged  on  to 
the  ship's  side.      The  form  cannot  well  be  developed,  so  that  the 


EER. 


FORECASTLE__DECK 


Fig.    150. 


BODY. 


SHEER. 


FO  R  EC  ASTLE___DECK_ 


1ULA 


( 


B 


UNIVERSITY 


WL\ 


ET 


Fig.    151. 


GUN  GALLERIES  OR  SPONSONS.  145 

loftsman  fits  up  section  moulds  on  the  sbip  at  each  frame,  from 
which  the  platers  make  their  own  templates.  This  form  may  also  be 
arranged  at  the  aft  end  in  the  same  manner.* 

Another  form  of   End  Gun  Gallery — sometimes  fitted.— 

Referring  to  Fig.  151,  make  A  B  and  A1  B1  of  equal  parallel  distance 
to  the  centre  line  of  the  ship,  and  draw  in  the  Body  the  moulded  form 
of  the  ship's  sections  above  the  load-line  relative  to  A1  B1.  Lift  these 
into  the  Half  Breadth  and  Sheer,  on  convenient  level  lines,  knuckle,  and 
rail.  Produce  the  level  lines  into  the  Sheer.  Fix  gun  position  0  and 
the  range  fore  and  aft,  make  D  E  F  a  fair  curve  suitable  to  work  gun 
at  range  and  depression.  Level  knuckle  sheers,  on  the  frames,  into  the 
Body,  and  lift  the  distance  of  D  E  F  from  A  B  on  each  frame,  and  set 
them  off  on  their  corresponding  sheer  levels  in  the  Body.  Make  the 
centre  section  E1  G  of  suitable  angle  to  ship's  side — the  point  Gr  is 
kept  well  above  the  load-line — and  produce  the  sheer  knuckle  points 
parallel  to  the  line  E1  G  to  meet  respective  frames  of  the  ship's  side. 
Then,  project  these  cutting  points  on  the  ship's  side  into  the  Sheer 
on  to  their  corresponding  frame  stations,  and  run  line  H  G1  K,  which 
is  the  form  line  in  the  Sheer.  Fair -up,  by  transferring  the  cutting 
points  on  each  level  line  from  A1  B1  of  the  Body  to  the  Half  Breadth, 
setting  them  out  on  their  stations  from  A  B.  The  terminations 
will  be  got  by  squaring  down  from  the  Sheer  on  to  the  Hah  Breadth 
corresponding  lines  H,  L,  M,  N,  0,  P,  Q,  and  K,  which  will  allow  the 
level  lines  to  be  drawn  in.  The  bulwark  is  made  perpendicular,  as 
shown  ;  and,  usually,  of  parallel  sheer  to  the  knuckle.  It  is  fitted  with 
hinged  doors  for  working  gun,  or  it  may  be  cut  away  in  the  manner 
of  the  dotted  line  R  S  T  to  suit  range  and  depression,  and  stiffened  on 
its  edge  with  angle  bar  and  half-round  moulding. 

Expansion  of  End  Gun  Gallery.  — Show  in  the  Body  the  set 
line  V  B1  square  to  E1  G  cutting  point  a.  Lift  from  B1  on  B1  V, 
points  a,  b,  c,  d,  c,  f,  and  g,  and  lay  them  off  on  the  expansion  frames, 
(ordinary  spacing)  on  the  line  A  B  produced,  V2  B2 ;  through  the  points 
a1,  b1,  c1,  etc.,  draw  in  h}  a\  Girth  this  line  around  c1,  station  96, 
for  the  frame  points  d1,  e1,/1,  g\  and  h\  and  lay  them  off  abaft  of  96 
on  V2  B2,  and  also  b1  and  a1  forward  of  96  in  the  same  manner.  Erect 
perpendiculars  through  spots  (dotted  lines),  which  are  the  expanded 
section  positions.  Lift  the  knuckle  points,  in  the  Body,  on  the 
stations  above  the  set  line  B*V,  and  place  them  on   the  expanded 

*  It  is  usual  to  give  90  degrees  range  forward  of  A  B,  so  that  direct  fore 
and  aft  fire  may  be  secured, 

11 


GUN  GALLERIES  OR  SPONSONS.  145 

loftsman  fits  up  section  ruouLls  on  the  ship  at  each  frame,  from 
which  the  platers  make  their  own  templates.  This  form  may  also  he 
arranged  at  the  aft  end  in  the  same  manner.* 

Another  form  of   End  Gun  Gallery — sometimes  fitted. — 

Kef  erring  to  Pig.  151,  make  A  B  and  A*BX  of  equal  parallel  distance 
to  the  centre  line  of  the  ship,  and  draw  in  the  Body  the  moulded  form 
of  the  ship's  sections  above  the  load-line  relative  to  A1  B1.  Lift  these 
into  the  Half  Breadth  and  Sheer,  on  convenient  level  lines,  knuckle,  and 
rail.  Produce  the  level  lines  into  the  Sheer.  Fix  gun  position  C  and 
the  range  fore  and  aft,  make  D  E  F  a  fair  curve  suitable  to  work  gun 
at  range  and  depression.  Level  knuckle  sheers,  on  the  frames,  into  the 
Body,  and  lift  the  distance  of  DEF  from  A  B  on  each  frame,  and  set 
them  off  on  their  corresponding  sheer  levels  in  the  Body.  Make  the 
centre  section  E1  G  of  suitable  angle  to  ship's  side — the  point  G-  is 
kept  well  above  the  load-line — and  produce  the  sheer  knuckle  points 
parallel  to  the  line  E1  G  to  meet  respective  frames  of  the  ship's  side. 
Then,  project  these  cutting  points  on  the  ship's  side  into  the  Sheer 
on  to  their  corresponding  frame  stations,  and  run  line  H  G1  K,  which 
is  the  form  line  in  the  Sheer.  Fair-up,  by  transferring  the  cutting 
points  on  each  level  line  from  A1  B1  of  the  Body  to  the  Half  Breadth, 
setting  them  out  on  their  stations  from  A  B.  The  terminations 
will  be  got  by  squaring  down  from  the  Sheer  on  to  the  Half  Breadth 
corresponding  lines  H,  L,  M,  N,  0,  P,  Q,  and  K,  which  will  allow  the 
level  lines  to  be  drawn  in.  The  bulwark  is  made  perpendicular,  as 
shown  ;  and,  usually,  of  parallel  sheer  to  the  knuckle.  It  is  fitted  with 
hinged  doors  for  working  gun,  or  it  may  lie  cut  away  in  the  manner 
of  the  dotted  line  B  S  T  to  suit  range  and  depression,  and  stiffened  on 
its  edge  with  angle  bar  and  half-round  moulding. 

Expansion  of  End  Gun  Gallery. — Show  in  the  Body  the  set 
line  V  B1  square  to  E1  G  cutting  point  a.  Lift  from  B1  on  B1  V, 
points  a,  b,  c,  d,  p,  /,  and  g,  and  lay  them  off  on  the  expansion  frames, 
(ordinary  spacing)  on  the  line  A  B  produced,  V2  B2 ;  through  the  points 
a1,  b1,  e\  etc.,  draw  in  h1  a\  Girth  this  line  around  c1,  station  96, 
for  the  frame  points  d1,  e1,/1,  g\  and  h1,  and  lay  them  off  abaft  of  96 
on  V2  B'2,  and  also  b1  and  a1  forward  of  96  in  the  same  manner.  Erect 
perpendiculars  through  spots  (clotted  lines),  which  are  the  expanded 
section  positions.  Lift  the  knuckle  points,  in  the  Body,  on  the 
stations  above  the  set  line  B^,  and  place  them  on   the  expanded 

*  It  is  usual  to  give  90  degrees  range  forward  of  AB,  so  that  direct  fore 
and  aft  fire  may  be  secured. 

11 


14G  NAVAL  ARCHITECTURE. 

frames  above  the  set  line  V2  B2,  viz.,  a2,  b2,  c2,  etc.  The  point  /r  may- 
be got  by  lifting  op  square  off  from  the  line  B1  V,  and  setting  it  out 
from  B2  V2.  Then  lift  the  distances  on  the  stations  below  B1  V  to 
ship's  side,  and  lay  them  off  below  the  set  line  in  the  expansion, 
through  which  points  draw  the  curve  a2,  c\  and  It2.  This  figure, 
Ir,  r,  a2,  c3,  is  the  expanded  form  below  the  knuckle :  allowance  must 
be  made  in  ordering  for  riveting  to  the  ship's  side  and  bulwarks. 

The  bulwark  plating  may  be  got  by  girthing  the  positions  of  the 
frames  and  butts  D  and  F  on  the  knuckle  line  D  E  F,  and  laying  them 
off  in  the  expansion  on  the  level  line  6,  about  (J(!  frame,  from  which  erect 
frame  perpendiculars,  and  on  them  set  off  above  level  line  the  sheer  of 
the  knuckle  on  each  frame.  A  curve  passed  through  these  spots  will 
give  expansion  of  the  knuckle  line,  and  the  rail  may  be  drawn  parallel 
to  this,  or  it  may  be  laid  off  independently  in  the  same  manner.  The 
butt  on  the  rail  edge  is  got  by  girthing  its  position  in  the  Half 
Breadth  on  each  side  of  E,  and  laying  it  off  about  96  on  the  rail 
expansion  line.  It  may  be  necessary  to  get  the  true  form  of  the  butt 
to  place  in  a  level  line  between  the  rail  and  knuckle. 


MOULDS.  147 


CHAPTER  XVII. 

Principal  Moulds  and  the  Order  they  are  sent  into  the  Yard — Stern  Posts- 
Stems— Stern  Tubes— Struts  -Beam  Camber—  Conning  Tower  — Pilot 
Bridge — Boat  Davits  and  Chocks. 


MOULDS. 

After  the  ship  is  faired-up  on  the  loft  floor  wood  moulds,  or 
templates,  are  supplied  for  constructing  many  of  the  parts.  Owing 
to  the  complexity  and  close  accuracy  required  in  war  ships  they  are 
more  numerous  than  in  merchant  work.  It  is  scarcely  possible  to 
state  all  the  moulds,  for  every  vessel  will  create  its  own  necessity;  hut 
the  following  are  some  of  the  principal  named  in  the  order  of  sending 
out. 

1.  Flat  keel  plate. 

2.  Vertical  centre  keelson. 

3.  Stem  and  stern  posts. 

4.  Stern  tubes  and  struts  in  twin  screws. 

5.  Beam  camber. 

6.  Longitudinals  and  armour  shelf. 

7.  Protective  deck  and  stringers. 

8.  Backing  plating. 

9.  Belt  or  side  armour. 

10.  Belt  deck. 

11.  Barbette  or  redoubts. 

12.  Gun  galleries. 

13.  Conning  tower. 

14.  Pilot  bridge. 

15.  Boat  davits  and  chocks. 

Nos.  1,  2,  5,  and  6  to  12,  are  explained  on  pages  79,  83,  34,  130, 
117,  119,  124  and  141.     The  remainder  will  now  be  briefly  described. 

Stern  Posts  are  made  of  solid  or  hollow  section  and  of  cast 
steel.  It  is  outside  of  the  province  of  this  treatise  to  give  the 
different  forms  of  sterns  which  are  adopted.  The  object  being 
simply  to  show  what  is  expected  from  the  loft  for  manufacturing 
purposes  ;  therefore,  only  one  form  of  post  is  given,  Fig.  152,  that  of 
a  vessel  with  twin  screws.     The  figure  shows  a  longitudinal  sectional 


148  NAVAL  ARCHITECTURE. 

elevation  drawn  by  the  loftsman  on  loose  hoards,  two  or  more, 
with  sections  at  various  points  C  I),  A  B,  K  L,  E  F,  H  J,  and  at  the 
frame  stations  1,  2,  3,  etc.  In  some  cases  a  rabbet,  single  or  double, 
is  made  in  the  casting  to  receive  the  shell  plating,  sufficiently  deep  to 
make  it,  when  in  position,  flush  with  the  extreme  side  of  post. 
Where  the  fore  and  aft  bottom  piece  is  of  considerable  length  an 
extra  stiffening  marked  G  is  cast  on  the  post — the  outline  is  shown 
by  dotted  lines  in  the  figure.  The  shell  plating  is  attached  to  this 
stiffener.  It  will  be  noted  that  the  sketch  shows  a  double  notch  for 
the  flat  keel  plates  :  this,  in  some  cases,  is  only  single  where  a  single 
plate  keel  is  fitted.  It  is  usual  to  indicate  on  the  moulds  the  position 
of  the  level  or  water-lines.  These  boards  are  sent  to  the  steel  works, 
or  yard  pattern  shop,  where  suitable  patterns  are  made  from  them 
for  casting  the  post. 

Stems  are  also  made  of  solid  or  IioHoav  section  and  of  cast  steel. 
Fig-  '53  is  a  full-sized  drawing  made  by  the  loftsman  on  loose  boards, 
showing  the  outside  and  inner  edges  and  rabbet-line,  etc.  It  is 
customary  to  cast  this  form  of  stem  in  two  pieces  with  a  V  keyed 
scarpli,  placed  on  or  about  the  load  water-line.  The  drawing  gives 
the  necessary  information  required  for  making  the  patterns.  A 
single  notch  is  shown  for  the  flat  plate  keel.  In  the  case  of  a  double 
plate  keel  another  notch  should  be  made.  War  vessels  are  generally 
fitted  with  flat  plate  keels. 

Stern  Tubes. — Almost  all  the  large  vessels  are  fitted  with  twin 
t  screws,  requiring  watertight  tubes  built  into  the  structure  where  the 
shafts  pass  through  the  ship's  sides.  They  are  sometimes  built  in  the 
ordinary  way,  with  plates  and  frame  bars  ;  the  frames  being  bossed 
in  and  out  to  suit  the  tube  and  a,  cast  steel  narrow  ring  fitted  at  each 
end  to  take  the  engineer's  brass  tube.  In  other  cases  a  steel  casting 
is  fitted  the  full  length,  with  ends  formed  as  in  Fig.  154,  and  the  part 
between  F  and  K  reduced  in  thickness  to  about  1  §  inches  similar  to 
Fig.  166.  Fig.  154  represents  another  method  of  construction.  The 
sectioned  ends  are  of  cast  steel  of  at  least  1^  inches  thick  at  any 
part.  A  complete  built  steel  tube  of  k  to  §  of  an  inch  thick  is 
placed  between  the  end  castings,  connected  by  a  lap  joint  ;  a  rabbet 
being  formed  for  the  purpose.  Cross  sections  are  given  at  various 
points  showing  how  the  shell  plating  is  attached  to  the  castings  and 
tube.  At  A,  N,  J,  and  L  partial  bulkheads  are  fitted,  to  which  palms 
from  the  castings  are  riveted.  At  the  after  end  there  is  a  projecting 
ledge,  with  a  notch  to  take  the  shell  plating.     The  frames  O,  G,  and 


V 


LlBRAfifT' 


Fig.    153 


CAST     STEM 


\L  SECTIO 


H 


154. 


ION    AT  QH 


154. 


\L  SECT10 


H 


N    AT  QH 


Fig.  154. 


MOULDS.  149 

R  are  bossed  in  to  the  shape  of  the  tube,  and  the  two  riveted  together 
about  P.  One  or  more  frames  are  cut  at  the  fore  end  to  allow  the 
withdrawing  of  the  engineer's  tube  and  stuffing  box  ;  fore-and-afters 
are  fixed  above  and  below  to  maintain  the  strength.  Just  abaft  of 
A  B  two  light  plates  S  are  placed  around  shaft  to  ease  the  corner. 
They  are  riveted  to  the  shell  and  A  B,  having  a  tapering  form  from 
A  B  to  the  aftermost  edge,  like  T  section.  The  space  behind  the 
plates  may  be  filled  in  with  light  wood. 

The  loftsman  supplies  the  pattern-makers,  for  casting  purposes, 
with  a  full-sized  drawing  of  the  sectioned  parts,  taken,  as  far  as 
possible,  square  off  :  and  sections  at  A  B,  C  I),  N,  E  F,  and  J  K, 
U  Y,  L  M,  having  winding  vertical  and  horizontal  lines  to  enable 
them  to  secure  the  proper  bevel  of  the  vessel's  side. 

Struts  or  After  End  Supports. — In  twin  screws  the  after 
ends  of  the  shafts  are  supported  by  projecting  arms  from  the  ship's 
side,  the  same  as  those  given  on  page  1G2  for  sheathed  vessels.  The 
upper  palms  are  commonly  attached  to  the  protective  deck  plating, 
or  a  special  saddle  plate  fitted  for  the  purpose. 

Beam  Camber. — Beam  moulds,  as  explained'  on  page  34,  are 
supplied  for  all  decks,  only  the  beam  arms  are  made  to  suit  the 
special  requirements  of  the  structure,  and  in  many  cases  for  a  double 
vertical  row  of  rivets.  The  camber  given  to  beams  is  not  quite  so 
much  as  that  required  by  the  Classification  Registry. 

Conning  Tower. — At  least  one  is  fitted  at  the  fore  end  on  the 
upper  or  spar  deck  just  abaft  of  the  barbette,  formed  as  shown  in 
sectional  plan  and  elevation,  Fig.  155.  The  armour  plating  varies 
from  i  to  10  inches  in  thickness,  and  is  supported  on  a  rigid  raised 
platform  attached  to  the  deck.  The  after  end,  as  seen  in  the  figure, 
has  an  open  entrance  of  about  20  inches,  protected  by  an  overlapping 
screen  of  slightly  thinner  armour.  The  vertical  edges  of  the  screen 
and  entrance  are  rounded  away.  The  main  part  is  formed  of  two 
plates  with  a  vertical  butt  at  the  centre  line,  attached  together  by  a 
vertical  key.  Sometimes  the  armour  is  carried  up  to  the  crown  plate 
and  attached  by  strong  bars.  This  crown  plate  is  about  2  inches 
thick.  The  armour  may  be  kept  short  of  the  top  to  get  a  thinner 
plate  between  it  and  the  crown  to  take  the  sight  holes.  These  holes 
are  24  inches  long  horizontally  and  3  inches  deep  vertically  ;  the 
centre  being  level  with  the  eye  of  an  average  man  when  standing. 

In  ordering  the  armour  plating,  a  full-sized  plan  showing  the 
butt  and  key-way,  is  scrieved  in  on  a  board  by  the  loftsman.     This  is 


LIB 


ERSJTY 


MOULDS.  149 

R  are  bossed  in  to  the  shape  of  the  tube,  and  the  two  riveted  together 
about  P.  One  or  more  frames  are  cut  at  the  fore  end  to  allow  the 
withdrawing  of  the  engineer's  tube  and  stuffing  box  ;  fore-and-afters 
are  fixed  above  and  below  to  maintain  the  strength.  Just  abaft  of 
A  B  two  light  plates  S  are  placed  around  shaft  to  ease  the  corner. 
They  are  riveted  to  the  shell  and  A  B,  having  a  tapering  form  from 
A  B  to  the  aftermost  edge,  like  T  section.  The  space  behind  the 
plates  may  be  filled  in  with  light  wood. 

The  loftsman  supplies  the  pattern-makers,  for  casting  purposes, 
with  a  full-sized  drawing  of  the  sectioned  parts,  taken,  as  far  as 
possible,  square  off  :  and  sections  at  A  B,  CD,  N,  E  F,  and  J  K, 
U  Y,  L  M,  having  winding  vertical  and  horizontal  lines  to  enable 
them  to  secure  the  proper  bevel  of  the  vessel's  side. 

Struts  or  After  End  Supports. — In  twin  screws  the  after 
ends  of  the  shafts  are  supported  by  projecting  arms  from  the  ship's 
side,  the  same  as  those  given  on  page  162  for  sheathed  vessels.  The 
upper  palms  are  commonly  attached  to  the  protective  deck  plating, 
or  a  special  saddle  plate  fitted  for  the  purpose. 

Beam  Camber. — Beam  moulds,  as  explained'  on  page  34,  are 
supplied  for  all  decks,  only  the  beam  arms  are  made  to  suit  the 
special  requirements  of  the  structure,  and  in  many  cases  for  a  double 
vertical  row  of  rivets.  The  camber  given  to  beams  is  not  quite  so 
much  as  that  required  by  the  Classification  Registry. 

Conning  Tower. — At  least  one  is  fitted  at  the  fore  end  on  the 
upper  or  spar  deck  just  abaft  of  the  barbette,  formed  as  shown  in 
sectional  plan  and  elevation,  Fig.  155.  The  armour  plating  varies 
from  4  to  10  inches  in  thickness,  and  is  supported  on  a  rigid  raised 
platform  attached  to  the  deck.  The  after  end,  as  seen  in  the  figure, 
has  an  open  entrance  of  about  20  inches,  protected  by  an  overlapping 
screen  of  slightly  thinner  armour.  The  vertical  edges  of  the  screen 
and  entrance  are  rounded  away.  The  main  part  is  formed  of  two 
plates  with  a  vertical  butt  at  the  centre  line,  attached  together  by  a 
vertical  key.  Sometimes  the  armour  is  carried  up  to  the  crown  plate 
and  attached  by  strong  bars.  This  crown  plate  is  about  2  inches 
thick.  The  armour  may  be  kept  short  of  the  top  to  get  a  thinner 
plate  between  it  and  the  crown  to  take  the  sight  holes.  These  holes 
are  24  inches  long  horizontally  and  3  inches  deep  vertically  ;  the 
centre  being  level  with  the  eye  of  an  average  man  when  standing. 

In  ordering  the  armour  plating,  a  full-sized  plan  showing  the 
butt  and  key-way,  is  scrieved  in  on  a  board  by  the  loftsman.     This  is 


Fig.     155. 
CONNING    TOWER 

FORE    k    AFT     ELEVATION 

DECK 


T^ 


IRON    PLATFORM 


BRACKETS 


DECK 


PLAN 


MOULDS.  151 

sent  with  the  finished  depth  to  the  manufacturers.  Where  the 
armour  is  carried  to  the  crown  plate,  the  position  of  the  sight  holes 
should  be  given  as  in  plan,  Fig.  155,  and  the  vertical  height,  with 
their  depth,  supplied  to  the  manufacturer.  A  template  of  the  seat 
for  the  armour  is  given  to  the  yard  to  form  platform. 

Pilot  Bridge. — This  is  laid  down  on  the  loft  floor  and  a  wood 
skeleton  template,  for  the  use  of  the  yard,  is  made  to  the  heel  of  the 
foundation  bar  for  one  side  of  the  ship  only.  If  there  is  much 
camber,  the  heel  line  should  be  expanded  and  a  camber  mould  supplied 
with  the  template. 

Boat  Davits  and  Chocks. — Occasionally  a  flat  wood  mould 
showing  the  edges  and  head  through  the  vertical  centre  is  supplied 
the  forge,  having  painted  on  at  various  points  of  the  length  the 
required  cross  section.  It  is  usual  in  this  case  to  lay  down  on  the 
loft  floor  the  plan  form  of  the  gunwale  and  the  half  sectional  form  of 
the  boat  at  the  davit  points.  Then  to  line  in  the  edges  of  the  davits 
for  making  the  moulds,  in  such  a  manner  that  there  will  be  room  for 
fenders,  and  to  get  the  boat  in  and  out  of  the  davits,  and  to  clear 
the  ship's  rail  and  side.  The  keel  of  the  boat  is  generally  arranged 
when  swinging  out,  12  inches  clear  of  the  rail ;  and,  the  broadest  beam, 
6  inches  clear  of  the  ship's  side  when  waterborne  at  the  load-line. 

Chock  moulds  to  the  inside  edge  are  made  for  all  boats  for  the 
use  of  the  forge  or  angle  smiths,  due  allowance  being  made  for 
padding.  These  should  be  accompanied  with  fore  and  aft  bevels  to 
suit  the  form  of  the  bottom  ;  the  points  chosen  are  indicated  on  the 
moulds. 

In  many  yards  a  figured  drawing  is  supplied  of  the  davits,  showing 
the  height,  outstretch,  radius,  and  diameter  at  different  parts,  with 
an  enlarged  figured  detail  sketch  of  the  head,  which  is  considered 
ample  for  their  construction. 


152  NAVAL   ARCHITECTURE. 


CHAPTEE  XVIII. 


To  Obtain  and  Line  off  the  Draught  Marks  on  Stem  and  Stern. 


DRAUGHT  MARKS. 

Draught  Marks. — These  are  placed  on  both  sides  of  the  stem 
and  stern,  by  means  of  which  the  draught  of  water  that  the  ship 
draws  at  any  time  when  afloat  may  be  correctly  ascertained.  In  some 
cases  the  metrical  system  is  applied  on  one  side  and  the  English  figures 
on  the  other.  Pig.  156  shows  the  method  of  lining  off  these  marks. 
Select  a  line  A  B,  square  to  the  load-line,  and  as  near  the  perpendicular 
as  possible.  Then  the  bottom  side  of  the  keel  F  is  produced  to  C. 
On  a  level  line  with  A  the  top  edge  of  two  straight  edges,  about 
12  by  Ik  inches  section,  are  fixed  level  across  the  ship,  at  a  short 
distance  apart,  D  and  E.  On  the  top  of  these  are  set  and  fixed  square 
to  load-line,  as  shown  in  half  cross  section,  two  long  measuring  laths, 
about  3  feet  apart ;  the  upper  part  being  attached  to  some  of  the 
staging  round  about.  The  duplicate  draught  marks  are  levelled  on  to 
the  ship's  side,  at  positions  D  and  E,  by  a  straight  edge  shown  in  the 
section  at  20  feet,  and  each  set  of  spots  connected  by  chalk  lines. 
Then  the  figures,  which  are  (3  inches  deep,  are  indicated  on  the  side 
about  A  B,  and  centre-punched.  Five  feet  is  about  as  low  as  they  will 
be  required.  The  process  is  repeated  on  the  other  side  of  the  vessel, 
and  the  after  end  marked  off  in  the  same  way. 


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154  NAVAL  ARCHITECTURE. 

"  OK   THE  ' 

UNIVERSITY 
_CAUFOft^i 

COMPOSITE    VESSELS, 


CHAPTER  XIX. 

Sheer  Draught— Extreme  Form  for  the  Calculation  of  Displacement— To  Find 
the  Heel  of  the  Frames  by  an  Approximate  Method — An  Exact  Method 
of  Finding  the  Heel  of  the  Frames— To  Find  the  Middle  Line  of  Rabbet 
—To  End  a  Level  Line  in  the  Half  Breadth  -To  Terminate  a  Frame  in 
the  Body — To  Find  the  Bearding  Line  approximately — To  Find  the 
Middle  Line  of  Rabbet  by  an  Exact  Method — To  Find  the  Bearding 
Line  by  another  Method — Form  of  the  Rabbet  in  the  Main  Keel  Piece — 
Working  Base  Line. 


Iii  composite  vessels  the  Sheer  Draught  is  made  to  the  outside  of 
the  planking.  This  is  faired-up  first  on  the  loft  floor,  and  the  dis- 
placement checked.  To  enable  you  to  place  the  form  of  the  frames  on 
the  scrieve  board,  it  is  necessary  to  remove  the  planking,  and  seeing 
it  is  made  of  almost  uniform  thickness  square  to  the  outside  surface, 
with  the  exception  of  the  topsides  and  the  extreme  ends,  it  will  be 
evident  that  it  is  a  variable  quantity  on  the  level  lines,  etc. 

To  Find  the  Heel  of  the  Frames.  — The  method  of  removal  of 
planking  is  simple  on  and  about  the  midship  section,  for  the  frame  is 
about  square  to  the  form  of  the  level  line  in  the  Half  Breadth.  In 
Fig.  157,  on  the  midship  frame  48,  set  in  square  to  the  outside  edge 
at  the  level  lines  and  buttocks,  the  thickness  of  the  plank  iv  o,  z  //,  ef, 
g  h,  and  pass  a  curve  through  the  points.  This  curve  is  the  inside  of 
the  plank,  or  the  heel  of  the  frame.  The  process  is  more  difficult  as 
you  approach  the  ends,  where  the  level  lines  cut  the  frame  stations 
obliquely  in  the  plan  and  sections.  A  quick  method  is  to  set  in 
square  to  the  outside  edge  at  the  several  level  lines  and  stations  in  the 
Half  Breadth  the  thickness  of  the  plank  -s  t  on  say  90  frame,  and 
transfer  the  distance  v  s  into  the  body  s1  r1,  square  to  the  section.  By 
this  means  a  sufficiency  of  spots  is  got  to  draw  in  S  T,  the  inside  of 
the  plank.  Then  the  cutting  points  on  the  level  and  buttock  lines 
are  lifted  into  the  Half  Breadth  and  Sheer  respectively,  and  the  inside 
form  faired-up  in  the  usual  way. 


f-r-t.^ 


ULL   LINES-OUTSIDE   OF    PLANKING. 
DOTTED    LINES-INSIDE   OF    PLANKING. 


BODY. 


Fig.    157. 


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DOTTED    LINES-INSIDE    OF    PLANKING. 


COMPOSITE  VESSELS.  155 

A  More  Exact  Method  of  Finding  the  Heel  of  the  Frames. 

— This  is  given  in  Professor  Rankine's  Shipbuilding,  Theoretical  and 
Practical.  It  is  the  one  which  has  been  adopted  in  large  shipbuilding 
establishments  for  many  years. 

In  Fig.  157,  ILL  is  a  level  line  showing  the  outside  of  the 
planking. 

At  the  point  B  and  b  erect  perpendiculars  B  A  and  b  a  to  4  L  L  and 
90  frame  respectively.  On  X  B  set  off  any  distance  X  C,  and  make 
x  c  equal  X  C.  Through  c  and  0  draw  c  a  and  C  A  perpendicular  to 
b  x  and  B  X,  cutting  b  a  and  B  A  at  a  and  A  respectively.  From  A 
draw  A  I)  perpendicular  to  A  B,  and  make  A  D  equal  to  a  c.  Join 
B  1).  Make  BR  equal  to  the  thickness  of  the  plank,  draw  RP 
parallel  to  DA,  then  P  is  the  horizontal  projection  of  a  point  in  the 
outer  surface  of  the  framing.  Draw  P  Q  parallel  to  A  C,  cutting  in 
Q.  In  the  body  make  xq  equal  XQ.  Draw  qp  perpendicular  to  bx, 
cutting  a  b  in  p,  then  p  is  the  vertical  projection  of  a  point  on  the 
outer  surface  of  the  frames,  P  being  its  horizontal  projection.  This 
point  is  not  situated  either  in  the  plane  of  the  level  line  or  that  of 
the  square  station  ;  it  is  therefore  necessary  to  find  similar  points 
as  shown  in  the  Fig.  157  for  each  frame  station,  then  a  curve  EF 
may  be  passed  through  these,  and  its- intersection  k,n,m,l,  with  the 
plane  of  each  level  line,  will  give  a  point  through  which  the  level  line 
will  pass.  The  distances  k,  n,  »i,  I,  on  each  section  are  measured 
off  and  transferred  into  the  Half  Breadth  on  their  corresponding 
stations,  and  curves  passed  through  the  points  k\  n\  m1,  I1  will  show 
the  form  of  the  inner  surface  on  the  level  lines.  The  buttock  heights 
may  also  be  lifted  to  the  dotted  or  inner  surface  and  transferred  into 
the  Sheer  and  the  ship  faired-up  on  these  new  lines. 

To  Find  the  Middle  Line  of  Rabbet. — Fig.  158  shows  part  of 
the  stem  and  the  fore  end  sections  drawn  to  the  plank  inside.  From 
the  point  B  in  the  Sheer  draw  B  D  square  to  the  fore  edge  of  the 
stem.  From  the  cutting  points  F,  E,  D,  and  G  the  outer  boundary 
line  of  the  plank,  erect  perpendiculars  D  H,  E  J,  etc.,  of  indefinite 
length.  Level  over  into  the  Body  on  to  their  respective  stations  the 
points  D,  E,  F,  G,  and  lift  the  distances  from  the  centre  line  and  lay 
D1  out  from  D  on  D  H,  E1  from  E  on  E  J,  F1  from  F  on  F  K,  and  G1 
from  G  on  G  L.  From  L,  which  is  the  half  siding  of  the  stem  at  G1, 
describe  a  circle  with  a  radius  L  N  equal  to  the  required  thickness  of 
planking  at  that  point.  Draw  LO  square  to  the  outside  surface, 
then  0  is  the  middle  of  the  rabbet,  which  allows  the  curve  H,  J,  K, 


LIBRAE 


■0151^ 


£**** 


Of 


COMPOSITE  VESSELS.  155 

A  More  Exact  Method  of  Finding  the  Heel  of  the  Frames. 

— This  is  given  in  Professor  Rankine's  Shipbuilding,  Theoretical  and 
Practical.  It  is  the  one  which  has  been  adopted  in  large  shipbuilding 
establishments  for  many  years. 

In  Fig.  157,  4LL  is  a  level  line  showing  the  outside  of  the 
planking. 

At  the  point  B  and  b  erect  perpendiculars  B  A  and  b  a  to  4  L  L  and 
90  frame  respectively.  On  X  B  set  off  any  distance  X  C,  and  make 
xc  equal  XC.  Through  c  and  C  draw  ca  and  C  A  perpendicular  to 
b  x  and  B  X,  cutting  b  a  and  B  A  at  a  and  A  respectively.  From  A 
draw  A  I)  perpendicular  to  A  B,  and  make  A  I)  equal  to  a  c.  Join 
B  I).  Make  BR  equal  to  the  thickness  of  the  plank,  draw  RP 
parallel  to  D  A,  then  P  is  the  horizontal  projection  of  a  point  in  the 
outer  surface  of  the  framing.  Draw  P  Q  parallel  to  A  C,  cutting  in 
Q.  In  the  body  make  xq  equal  XQ.  Draw  qp  perpendicular  to  b  x, 
cutting  a  b  in  p,  then  p  is  the  vertical  projection  of  a  point  on  the 
outer  surface  of  the  frames,  P  being  its  horizontal  projection.  This 
point  is  not  situated  either  in  the  plane  of  the  level  line  or  that  of 
the  square  station  ;  it  is  therefore  necessary  to  find  similar  points 
as  shown  in  the  Fig.  157  for  each  frame  station,  then  a  curve  EF 
may  be  passed  through  these,  and  itsr  intersection  k,n,m,l,  with  the 
plane  of  each  level  line,  will  give  a  point  through  which  the  level  line 
will  pass.  The  distances  k,  n,  in,  I,  on  each  section  are  measured 
off  and  transferred  into  the  Half  Breadth  on  their  corresponding 
stations,  and  curves  passed  through  the  points  k1,  n1,  m1,  I1  will  show 
the  form  of  the  inner  surface  on  the  level  lines.  The  buttock  heights 
may  also  be  lifted  to  the  dotted  or  inner  surface  and  transferred  into 
the  Sheer  and  the  ship  faired-up  on  these  new  lines. 

To  Find  the  Middle  Line  of  Rabbet. — Fig.  158  shows  part  of 
the  stem  and  the  fore  end  sections  drawn  to  the  plank  inside.  From 
the  point  B  in  the  Sheer  draw  B  D  square  to  the  fore  edge  of  the 
stem.  From  the  cutting  points  F,  E,  D,  and  G  the  outer  boundary 
line  of  the  plank,  erect  perpendiculars  D  H,  E  J,  etc.,  of  indefinite 
length.  Level  over  into  the  Body  on  to  their  respective  stations  the 
points  D,  E,  F,  G,  and  lift  the  distances  from  the  centre  line  and  lay 
D1  out  from  D  on  D  H,  E1  from  E  on  E  J,  F1  from  F  on  F  K,  and  G1 
from  G  on  G  L.  From  L,  which  is  the  half  siding  of  the  stem  at  G1, 
describe  a  circle  with  a  radius  L  N  equal  to  the  required  thickness  of 
planking  at  that  point.  Draw  L  0  square  to  the  outside  surface, 
then  0  is  the  middle  of  the  rabbet,  which  allows  the  curve  H,  J,  K, 


156  NAVAL  AKCHITECTURE. 

0,  the  inner  surface  of  the  plank,  to  be  drawn  in.  This  process  is 
repeated  at  A  and  0,  at  the  load-line,  and  sections  abaft  of  A.  A 
line  run  through  the  points  so  found  will  give  the  rabbet  at  any 
section,  shown  by  dotted  line. 

To  End  a  Level  Line  in  the  Half  Breadth. — An  easy  way 
is  to  draw  in  the  Sheer  S  T  through  the  extreme  points  d,  e,  /,  g,  and 
li,  and  W  Y  through  the  corresponding  edge.  Project  down  into  the 
Half  Breadth  on  to  the  centre  the  intersection  of  the  outer  boundary 
line  or  fore  edge  of  the  rabbet,  and  set  off  on  these  the  half  siding  of 
the  stem,  through  which  draw  parallel  lines  to  the  centre.  Then 
square  down  from  1  level  line  the  points  a,  r,  d  on  to  its  parallel  hue, 
and  mark  out  an  ellipse  through  the  points,  the  cross  width  will  equal 
Xx.     The  inner  surface  should  terminate  at  b1  on  the  edffe  of  the 

o 

ellipse.     The  same  process  can  be  repeated  at  each  level  line. 

To  Terminate  a  Frame  in  the  Body. — Level  over  from  the 
Sheer  in  Fig.  158  the  points  of  intersection  m,  n,  p,  G,  of  say  97 
frame,  with  S  T,  W  V,  middle  rabbet,  and  boundary  line.  Draw  in 
an  ellipse  in  the  same  manner  as  before  described  for  the  level  line. 
Then  97  frame  will  terminate  tangent  to  this,  or  the  middle  rabbet 
levelled  over. 

To  Find  the  Bearding  Line.  —  In  Fig-.  158,  produce  L  parallel 
to  the  centre  B  D  until  it  cuts  the  curve  H  K  0,  then  make  M  N 
square  to  B  D  ;  N  is  a  point  on  B  D  for  the  bearding  line.  This  is 
done  at  each  section  until  a  sufficient  number  of  spots  is  secured  to 
draw  line  in.  It  may  require  some  modification  above  the  load-line  to 
get  a  good  connection  for  the  planking. 

To  Find  the  Middle  Line  of  Rabbet  by  another  Method.* 
— In  Fig.  160.  Let  a  b  and  a2  b"  be  the  vertical  traces  of  a  level 
plane,  and  let  a1  b1  be  the  projection  in  the  Half  Breadth  of  its 
intersection  with  the  surface  of  the  plank.  At  the  "point  b,  where 
the  level  line  in  the  Sheer  cuts  the  fore  edge  of  the  rabbet, 
draw  a  tangent  line  c  d  to  that  curve,  cutting  the  base  line  of  the 
Sheer  at  the  point  d.  Project  the  point  d  upon  the  middle  line  of 
the  Half  Breadth  at  d\  from  which  draw  the  perpendicular  dlg, 
making  d1  g  =  to/1//1  iu  the  Body.  Then  //  is  the  horizontal  trace 
of  the  tangent  to  the  fore  end  of  rabbet  at  b.  Through  b\  the  fore 
edge  of  the  rabbet  in  the  Half  Breadth,  at  the  height  of  the  level 
line  a1  b\  draw  a  tangent  //  k  to  the  latter  line,  cutting  the  middle  line 

*  Taken  from  Professor  Rankine's  Shipbuilding,  Theoretical  and  Practical. 


BODY 


The  boundary  line,  or  fore  edge  of  rabbet,  is  A. 

The  middle  line  of  rabbet  is  B. 

The  bearding  line,  or  after  edge  of  rabbet,  is  C 


95  9*  95 


"»       nr 


Fig.    158 


The  boundary  line,  or  fore  edge  of  rabbet,  is  A 

The  middle  line  of  rabbet  is  B. 

The  bearding  line,  or  after  edge  of  rabbet,  is  C 


COMPOSITE  VESSELS.  157 

in  r1,  which  point  project  upon  the  level  line  in  the  Sheer  at  v. 
Also  through  the  point  g,  draw  Im  parallel  to  It  k,  cutting  the  middle 
line  at  n\  which  point  project  upon  the  base  line  of  the  Sheer  at  n. 
Join  n  v,  then  the  line  a  v  is  the  vertical  trace  of  the  tangent  plane 
to  the  surface  of  the  ship  at  b,  b1.  Through  b  and  b1  draw  b  p  and 
bx  />l  perpendicular  to  n  v  and  n1 I  respectively,  that  is,  to  the  vertical 
and  horizontal  traces  of  the  tangent  plane.  Therefore  b  p  and  b1  pl 
are  the  vertical  and  horizontal  projections  of  a  perpendicular  to  the 
tangent  plane  at  the  point  b,  b1.  Take  any  point,  p,p\  in  the  per- 
pendicular, and  consider  for  the  present  that  the  plane  of  the  level 
line  'i  b  is  the  horizontal  plane  of  projection.  Through  p1  draw  p1  s1 
perpendicular  to  p1  b1,  and  make  pl  s1  =  to  p  s  in  the  Sheer.  Join 
61s1,  this  is  the  rebatment  on  the  horizontal  plane  of  a  line  per- 
pendicular to  the  tangent  plane  at  b,  b1.  Set  off  on  bl  s1  the  distance 
b1 1  equal  to  the  thickness  of  the  bottom  plank,  and  through  t  draw 
tt\  parallel  to  s1p1,  cutting  bx  pl  at  t1,  then  i1  is  the  horizontal  projection 
of  a  point  in  the  middle  of  the  rabbet.  By  projecting  the  point  if1  upon 
the  line  b  p  a  point  f  is  found  in  the  vertical  projection  of  the  middle 
of  rabbet.  Similarly,  the  point  f  may  be  projected  over  the  Body 
at  t3.  Other  points  in  the  middle  of" rabbet  having  been  found  in  the 
three  plans,  the  line  of  the  middle  of  rabbet  can  be  drawn,  and  all  the 
level  lines  in  the  Sheer  and  Body  will  end  at  their  intersections  with 
it.  These  endings  can  then  be  projected  into  the  Half  Breadth,  and 
the  level  lines  in  that  plan  ended  at  the  points  given  thus. 

To  Find  the  Bearding  Line  by  another  Method.  —  Tn  Fig. 
1 60  draw  in  the  Half  Breadth  short  lines  parallel  to  the  middle 
line  of  that  plan  bl  "W,  and  at  a  distance  from  it  equal  to  the  half- 
siding  of  the  stem  at  each  of  the  level  lines,  the  points  where  these 
lines  intersect  the  corresponding  level  lines,  of  the  inner  surface  of  the 
plank,  will  be  in  the  horizontal  projection  of  the  bearding  line,  and 
the  vertical  projection  of  that  line  is  found  by  projecting  these  inter- 
sections W  upon  the  corresponding  level  lines  W1  in  the  Sheer,  and 
passing  a  curve  through  the  points  W1,  etc.,  so  obtained. 

Form  of  the  Rabbet  in  the  Main  Keel  Piece. — In  Fig.  161 
from  the  outer  boundary  point  A  describe  circle  C  J  B  equal  in  radius 
to  the  thickness  of  the  plank  at  that  part,  which  is  usually  slightly 
thicker  than  the  other  planking.  Produce  the  inner  surface  of  the 
planking  L  N  tangent  to  the  circle  cutting  at  C.  Join  C  to  A. 
Continue  E  A  to  J,  and  draw  J  M  level.     Then  J  M  is  the  top  of  the 


COMPOSITE  VESSELS.  157 

in  r\  which  point  project  upon  the  level  line  in  the  Sheer  at  v. 
Also  through  the  point  g,  draw  Im  parallel  to  h  ]>,  cutting  the  middle 
line  at  n\  which  point  project  upon  the  base  line  of  the  Sheer  at  n. 
Join  n  v,  then  the  line  n  v  is  the  vertical  trace  of  the  tangent  plane 
to  the  surface  of  the  ship  at  b,  b1.  Through  b  and  b1  draw  b  p  and 
bx  /i1  perpendicular  to  n  v  and  n1 1  respectively,  that  is,  to  the  vertical 
and  horizontal  traces  of  the  tangent  plane.  Therefore  b  p  and  frp1 
are  the  vertical  and  horizontal  projections  of  a  perpendicular  to  the 
tangent  plane  at  the  point  b,  b1.  Take  any  point,  p,  p1,  in  the  per- 
pendicular, and  consider  for  the  present  that  the  plane  of  the  level 
line  'i  b  is  the  horizontal  plane  of  projection.  Through  p1  draw  p1  s1 
perpendicular  to  p1  b1,  and  make  p1  s1  =  to  p  s  in  the  Sheer.  Join 
61s1,  this  is  the  rebatment  on  the  horizontal  plane  of  a  line  per- 
pendicular to  the  tangent  plane  at  b,  b1.  Set  off  on  b1  s1  the  distance 
b1 1  equal  to  the  thickness  of  the  bottom  plank,  and  through  t  draw 
tt\  parallel  to  s1p1,  cutting  bl  p1  at  t\  then  i1  is  the  horizon  f/tl  projection 
of  a  point  in  the  middle  of  the  rabbet.  By  projecting  the  point  ^npon 
the  line  b  p  a  point  f  is  found  in  the  vertical  projection  of  the  middle 
of  rabbet.  Similarly,  the  point  f  may  be  projected  over  the  Body 
at  /3.  Other  points  in  the  middle  or  rabbet  having  been  found  in  the 
three  plans,  the  line  of  the  middle  of  rabbet  can  be  drawn,  and  all  the 
level  lines  in  the  Sheer  and  Body  will  end  at  their  intersections  with 
it.  These  endings  can  then  be  projected  into  the  Half  Breadth,  and 
the  level  lines  in  that  plan  ended  at  the  points  given  thus. 

To  Find  the  Bearding  Line  by  another  Method.  —  In  Fig. 
1 60  draw  in  the  Half  Breadth  short  lines  parallel  to  the  middle 
line  of  that  plan  b1  W,  and  at  a  distance  from  it  equal  to  the  half- 
siding  of  the  stem  at  each  of  the  level  lines,  the  points  where  these 
lines  intersect  the  corresponding  level  lines,  of  the  inner  surface  of  the 
plank,  will  be  in  the  horizontal  projection  of  the  bearding  line,  and 
the  vertical  projection  of  that  line  is  found  by  projecting  these  inter- 
sections W  upon  the  corresponding  level  lines  W1  in  the  Sheer,  and 
passing  a  curve  through  the  points  W1,  etc.,  so  obtained. 

Form  of  the  Rabbet  in  the  Main  Keel  Piece. — In  Fig.  161 
from  the  outer  boundary  point  A  describe  circle  C  J  B  equal  in  radius 
to  the  thickness  of  the  plank  at  that  part,  which  is  usually  slightly 
thicker  than  the  other  planking.  Produce  the  inner  surface  of  the 
planking  L  N  tangent  to  the  circle  cutting  at  C.  Join  C  to  A. 
Continue  E  A  to  J,  and  draw  J  M  level.     Then  JM  is  the  top  of  the 


CD 

oh 
il 


COMPOSITE  VESSELS.  159 

main  keel  piece.  Continue  inner  thickness  line  F  G  to  cut  A  C. 
Then  D  is  the  middle  of  the  rabbet.  Join  D  to  J,  which  gives 
ADJ  the  form  of  the  rabbet  for  the  thick  garboard  strake. 

Working  Base  Line. — Level  J  extreme  height  of  the  circle 
C  J  B  on  to  the  centre  line,  then  M  K  is  the  position  of  the  conven- 
tional base  line  for  laying  off,  which  is  produced  fore  and  aft  on  the 
loft  floor. 


160  NAVAL  ARCHITECTURE. 


SHEATHED    VESSELS. 


CHAPTER  XX. 

Alteration  of  Practice — Thickness  of  Wood  Sheathing — Thickness  of  Shell 
Plating  -Method  of  Fastening  — Solid  Stems  and  Stern  Posts — Hollow 
Section  Stems  and  Stern  Posts— Method  of  Housing,  Planking  and 
Shell  Plating  —Connection  of  Keel — Finish  of  Planking  and  Plating  on 
the  Stern — Stern  Post  of  a  Cruiser — Stem  of  a  Cruiser — Shaft  Brackets 
or  Struts — Method  of  Attachment  at  Head  and  Foot — Necessary  Moulds 
—  Stern  Tubes  in  Twin  Screws — How  to  House  Planking  and  Shell 
Plating  —Bossing  of  Frames — Necessary  Moulds— Stern  Posts  in  Single 
Screw  Vessels— System  of  Terminating  Planking,  Shell  Plating,  and 
Keel — Necessary  Moulds  for  Casting —Rabbet  in  the  Main  Keel  Piece 
— Taking  Off  the  Planking  and  Shell  Plating. 


The  practice  of  double  planking,  adopted  in  composite  vessels,  for 
so  many  years  by  the  British  and  other  navies,  is  giving  pla.ce  to 
single  planking  of  3|  to  4  inches,  placed  on  top  of  a  steel  shell  of  at 
least  a  ^  of  an  inch  thick.  This  planking,  which  is  formed  of  12 
inch  strakes,  is  attached  to  the  plating  between  the  frames  by  |-  of 
an  inch  forged  naval  brass  bolts,  tapped  through  the  plating,  and 
having  a  grummet  and  steel  washer  under  the  nut  of  the  bolt  on  the 
inside.  The  lap  edges  of  the  plates  are  generally  made  single,  and 
the  butts  double  riveted.  This  planking  extends  above  the  load-line 
amidships  for  about  2  feet,  and  at  the  forward  and  after  ends  5 
and  3  feet  respectively.  Solid  stern  posts  and  stems  of  gun-metal  or 
phosphor  bronze  have  been  fitted,  but  these  are  giving  place  to  hollow 
sections,  as  shown  by  Figs.  162  and  163,  made  of  gun-metal.  In 
settling  the  size  of  the  section,  care  should  be  exercised  on  the  loft 
floor  to  keep  the  moulded  line  produced  about  1  inch  from  the  centre 
line  at  the  fore  edge  of  the  posts  to  allow  room  for  riveting  shell  to 
the  casting.  The  shell  plating  is  rabbeted  on  to  the  post  as  shown, . 
and  provision  is  made  for  housing  the  planking,  so  that  it  is  flush 
with  the  outside  of  the  casting.  The  keel  piece  of  the  post  has  a 
notch  for  receiving  the  flat  plate  keel,  and  a  shoe  A  for  securely 
attaching  the  main  keel  piece.  Fig.  162  is  the  stern  post  of  a  cruiser 
with   twin   screws,   and  a  recess  is   provided   in    the   sole-piece  for 


CRO 


[Op 


Fig.  162. 


3N-POST    OF    A    SHEATHED    CRUISER. 


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Fig.  162. 
CAST    STERN-POST    OF    A    SHEATHED    CRUISER. 


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NAVAL  ARCHITECTURE. 


receiving  the  after  brackets  or  struts,  fitted  for  the  support  of  the 
end  of  the  screw  shafts,  the  connection  of  which  will  be  seen  by 
reference  to  Fig.   164. 

By  one  of  the  detail  sections  of  Fig.  162  it  will  be  noted  that  a 
vertical  centre  plank  is  worked  up  the  stern  plate  from  the  stuffing 
box  projection  to  the  top  to  receive  the  plank  ends. 

Shaft  Brackets  or  Struts  Aft. — Occasionally  these  are  made 
in  one  piece,  but  a  more  general  practice  seems  to  be  to  fit  them,  as 
shown  by  Fig.  164,  with  a  V  scarph  over  the  keel.  This  method 
allows  easy  adjusting  for  the  shaft  centres.  The  upper  palms  are 
attached  to  the  protective  deck,  or  a  strong  saddle-back  between 

Fig.    165. 

PORt   k  AFT    VIEW 
Of       PALM 


partial  bulkheads.  They  may,  where  found  necessary,  be  fitted  with 
a  double  palm  as  in  Fig.  165.  A  watertight  collar,  in  two  pieces,  is 
worked  on  the  shell  plating  round  the  struts  ;  the  flange  being  made 
sufficiently  deep  to  take  the  wood  sheathing  as  shown. 

To  make  the  patterns  for  casting,  the  loftsman  supplies  a  drawing, 
on  loose  boards,  of  a  vertical  cross  section  through  the  centre  of  the 
strut,  with  the  centre  of  shaft  and  fore  and  aft  bevels  for  the  palms. 
A  small  detailed  figured  drawing  is  given  with  the  mould,  which 
enables  patterns  to  be  made. 

Stern  Tubes  in  Twin  Screw  Vessels. — These  tubes  are  made 
of  gun-metal,  as  in  Fig.  1 66,  shown  by  sectioned  parts.     Provision  is 


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163 


made  for  housing  the  wood  planking  and  shell  plating  with  watertight 
connection.  They  are  attached  by  projecting  palms  to  partial  bulk- 
heads, shown  at  A  B,  F  E,  and  J  K  sections.  The  intermediate 
frames  between  H  and  K  are  bossed  in,  as  seen  in  section  G  H,  and  a 
connection  to  tube  made  at  P.  Those  forward  of  K  J  are  bossed  out 
sufficiently  to  allow  the  withdrawing  of  the  engineer's  tube,  etc.,  or 
one  or  two  frames  are  cut  to  save  excessive  bossing,  and  fore  and 
afters  fitted  to  maintain  rigidity.  The  after  end  has  a  projecting 
flange  L,  with  a  notch  for  taking  shell  plating  and  housing  planking  ; 

Fig.    169. 


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this  is  carried  round  the  full  length  of  the  tubes  as  indicated  by  the 
sections  at  different  points.  The  form  of  the  frames  in  way  of  the 
tubes  are  scrieved  in  on  the  boards,  after  fairing  up  on  the  loft  floor. 
The  loftsman  supplies,  on  a  board,  the  pattern-makers  with  a  longi- 
tudinal section  of  the  sectioned  parts,  together  with  the  cross  sections, 
as  represented,  having  marked  on  them  vertical  and  horizontal  wind- 
ing lines  to  get  the  correct  bevel  of  the  ship's  side.  The  pattern  is 
usually  carefully  checked  by  the  loftsman  before  being  sent  away. 


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made  for  housing  the  wood  planking  and  shell  plating  with  watertight 
connection.  They  are  attached  by  projecting  palms  to  partial  bulk- 
heads, shown  at  A  B,  F  E,  and  J  K  sections.  The  intermediate 
frames  between  H  and  K  are  bossed  in,  as  seen  in  section  G  H,  and  a 
connection  to  tube  made  at  P.  Those  forward  of  K  J  are  bossed  out 
sufficiently  to  allow  the  withdrawing  of  the  engineer's  tube,  etc.,  or 
one  or  two  frames  are  cut  to  save  excessive  bossing,  and  fore  and 
afters  fitted  to  maintain  rigidity.  The  after  end  has  a  projecting 
flange  L,  with  a  notch  for  taking  shell  plating  and  housing  planking  ; 

Fig.    169. 


this  is  carried  round  the  full  length  of  the  tubes  as  indicated  by  the 
sections  at  different  points.  The  form  of  the  frames  in  way  of  the 
tubes  are  scrieved  in  on  the  boards,  after  fairing  up  on  the  loft  floor. 
The  loftsman  supplies,  on  a  board,  the  pattern-makers  with  a  longi- 
tudinal section  of  the  sectioned  parts,  together  with  the  cross  sections, 
as  represented,  having  marked  on  them  vertical  and  horizontal  wind- 
ing lines  to  get  the  correct  bevel  of  the  ship's  side.  The  pattern  is 
usually  carefully  checked  by  the  loftsman  before  being  sent  away. 


1  64  NAVAL  ARCHITECTURE. 

Stern  Posts  in  Single=screw  Vessels. — They  have  been  fitted 
in  two  pieces,  as  in  Fig.  167,  the  sole-piece  being  keyed  at  C  into  the 
stern  post— shown  in  section  through  the  key-way — and  scarphed  at 
D.  The  head  of  the  post  is  attached  to  a  strong  horizontal  plate  by 
a  vertical  T  bracket.  The  rudder  post,  of  wood,  is  fitted  into  a  hollow 
piece  cast  on  the  sole-piece.  The  planking  and  shell  plating  is 
rabbeted  into  the  head  of  the  stern  post.  Provision  is  made  for 
securing  the  planking  and  shell  plating,  as  shown  by  section  through 
A  B.  The  fore  end  of  the  sole-piece  is  made  with  a  shoe  and  notch 
to  take  the  main  wood  and  flat  plate  keel. 

A  better  method  is  that  given  in  Fig.  168,  where  the  brass  casting 
is  in  one  piece.  The  sections  show  clearly  the  character  of  the  post, 
and  the  way  of  terminating  the  shell  plating  and  planking.  For 
making  the  patterns  a  full-sized  drawing,  as  shown,  is  given  by  the 
loft,  with  sections  at  different  points  of  the  keel  piece,  and  others  at 
the  level  lines,  a  few  through  the  arch  over  the  aperture,  and  about 
three  cross  sections  through  the  head  piece. 

Rabbet  in  the  Main  Keel  Piece. — Referring  to  the  Fig.  169. 
From  the  point  A,  with  A  D  radius,  equal  to  the  thickness  of  the 
planking  and  the  garboard  shell  plating,  describe  circle  BDG. 
Produce  moulded  line  E  on  the  heel  of  the  frame,  tangent  to  this 
circle,  cutting  say  at  C,  join  A  to  C.  Line  in  the  flat  plate  keel  as 
shown,  then  A  C  is  the  line  of  the  rabbet  for  terminating  the  planking. 

Takingf^ff  the  Planking,  etc. — The  planking  and  shell  plating 
are  taken  off  in  the  same  manner  as  explained  on  page  154  for 
composite  vessels. 


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INDEX 


After  bossed  frames,  12,  14 

„      end  finish,  16 

,,      end  floors,  38 

,,      end  supports  for  shafts,  77,  149 
Allowance  for  beam  arms,  88 
Alteration    of     practice    in    sheathed 

ships,  160 
Appearance  of  lines  in  sheer  draught,  2 
Applying  frame  bevels,  63 
Approximate  sheer  line,  20 
Area  of  inner  bottom  plating,  42 
,,      outer  bottom  plating,  49 
Armour  barbette,  124 

,,        belt,  battle  ship,  119 

,,        belt  connection,  120 

,,        belt  framing,  119 

,,        conning  tower,  149 

,,        in  battle  ship,  119 

,,        in  cruiser,  114 
shelf,  119 

,,        turret,  126 

Ballast  tank,  cellular  bottom,  41 
,,         tank,  Mclntyre  type,  44 
,,         tank,  Swan  type,  44 
Barbette  of  circular  form,  126 
,,         of  egg  form,  124 
,,         structure,  124 
Base  line  in  sheer  draught,  7,  159 
Battle  ship's  belt  deck,  1 1 9 

,,  inner  bottom,  137 

,,  protective  deck.  121 

,,  side  armour,  119 

Beam  arm  allowance,  88 
,,      bevels,  war  vessels,  118 
,,      camber,  merchant  ships,  6,  34 
,,      camber,  war  vessels,  149 
moulded,  3 


Beams  protective  deck,  118 

Bearding  line,  approximate,  composite 

vessels,  156 
Bearding   line,    accurately,   composite 

vessels,  157 
Bell- mouthed  cargo  hatches,  102 
Belt  armour  battle  ship,  119 
,,  correction,  119 

.,  expansion,  123 

,,  fairing,  123 

,,  moulds,  124 

Belt  deck  construction,  119 
Best  lines  for  fairing -up,  8 

,,     position  for  bilge  keels,  128 
Bevelling  board  for  harpins,  70 
Bevelling  machine,  63 
Bevels  for  frames,  62 

,,         inner  bottom  frames,  139 
,,         war  ship's  beams,  118 
Bilge  diagonal,  8 
,,    keels,  128 
,,    turn,  6 
Boat  beam  moulds,  84 

,,    davitsand  chocks,  war  vessels,  151 
Body  plan  explained,  2 
,,  fairing-up,  7 

Bossed  frames,  aft,  12,  14 
,,  at  ram,  129 

,,  sheathed  ships,  163 

Bossing  twin  screws,  12,  148,  163 
Bottom  plating  area,  42,  48,  132 

,,        rise,  5 
Bow  and  buttock  lines,  11 
Box  framing,  battle  ships,  121 
Brackets  for  struts,  77,  149,  162 
Bridge  mould,  151 
Butts  of  belt  deck,  121 

,,       protective  deck,  118 


166 


INDUX. 


Calculation  of  shaft  passage  plating, 
104 

Camber  of  beam  allowed,  34 

,,  in  war  vessels,  149 

, ,  methods  of  laying  off,  34 

Cant  frames  aft,  32 

,,  forward,  27 

,,  ,,       expanded,  27 

,,  moulds,  33 

Cant  knees  on  scrieve  board,  58 
Cargo  hatches,  bell-mouth  type,  102 

,,  ordinary  type,  101 

Cellular  double  bottom,  41 
Centre  through  plate  keelson  mould,  83 
Change  of  frames,  6 
Check  on  stern  expansion,  51 
Checking  frame  bevels,  63 

keel,  110 
Chocks  for  boats  in  war  vessels,  151 
Circular  barbette,  126 
Classification  depth,  6 
,,  length,  6 

Clipper  type  of  stem,  107 
Common  harpin,  69 
Composite  vessels,  154 
Conical  ballast  tank,  Swan's,  44 

„       gun  gallery,  142 
Connection  of  belt  deck,  119 

,,  sheathed  ship's  keels,  163 

Conning  tower,  149 
Construction  of  belt  deck,  119 

,,  sheer  diagram,  22 

Contracted  method  of  fairing,  10 
Correct    method    of    protective    deck 

expansion,  117 
Correction  for  belt  armour,  119 
Cruiser's  armour,  114 

,,  protective  deck,  114 

Curved  floors,  37 
Cutting  hawse  pipe  holes,  102 
Cut- water,  107 

Davits  for  war  ship's  boats,  151 
Deadflat,  5 

Deck  houses  of  iron,  100 
,,      lines  on  scrieve  board,  56 


Deck  plate  edges,  36 
ribbands,  68 
sheer  at  side,  35 
stringer  plate  expansion,  35,  88 
surface-expanded,  35 
wide  stringer  plates,  36 
Definition  of  bilge  diagonal,  11 

,,  bow  line  and  buttock,  11 

,,  fair  line,  9 

,,  fairness,  9 

Depth  by  classification,  6 
,,      moulded,  5 
,,       of  hold,  6 
Detective  bevelling  machine,  63 
Diagonal  cutting  knuckle,  20 
Diagonals,  8 

Diagrams  for  sheer  line,  22 
Diminishing  line  of  floors,  37 
Double  bottom  expansion,  42 
,,  ,,      floors,  44 

,,  ,,      frame  bevels,  139 

,,  ,,      margin  plate,  43 

,,      bottoms,  41,  130 
,,      cellular  bottom,  41 
,,      Mclntyre  bottom,  44 
,,      Swan  bottom,  44 
Doubling  of  masts  at  deck,  92 
,,  ,,  heel,  92 

Draft  marks,  merchant,  108 
,,  war  vessel,  152 

Drawing  in  deck  at  side,  35 
,,  sheer-draught,  7 

Edges  of  belt  deck,  121 
,,  deck  plating,  36 

, ,  outer  bottom  plating,  45 

Ellipse,  113 

End  armour,  battle  ship,  121,  122 
,,     floors,  38 

,,     of  level  line  in  half  breadth,  8,  156 
Exact    method     of     finding     heel     of 

frames  in  composite  vessels,  155 
Expansion  of  armour  belt,  123 

,,  barbette  armour,  124 

,,  battle      ship's       inner 

bottom,   139 


INDEX. 


167 


Expansion  of  cargo  hatches,  101,  102 
,,  conical  gun  gallery,  143 

,,  deck  stringer  plate,  88 

,,  deck  surface,  35 

,,  double  bottom  floors,  44 

,,  end  gun  gallery,  145 

,,  forward  cants,  27 

,,  inner  bottom,  cruiser,  132 

,,  inner  bottom  plating,  42, 

139 
,,  iron  deck  house,  100 

,,  longitudinals,  cruiser,  132 

,,  longitudinals   on   curved 

diagonals,  133 
,,  margin  plate,  43 

,,  mast  plating,  91 

,,  midship  gun  gallery,  141 

,,  poop  round,  86 

,,  protective  deck,  115 

,,  rudder  trunk,  96 

,,  shaft  tunnel,  104 

,,  sheer  harpin,  70 

shell,  48,  49 
,,  shell  plate,  50 

,,  stern ,  51 

,,  stern  of  ordinary  type,  51 

,,  thin  plates  of   barbette, 

124 
,,  tumble-home  stern,  53 

,,  turned  up  floors,  38 

,,  turtle  back,  87 

Explanation  of  body  plan,  2 

,,  half  breadth  plan,  2 

,,  profile,  2 

,,  sheer  draught,  1 

,,  terms  used,  3 

Extra  length  to  form  beam  arms,  88 
Extreme  end  floors,  38,  44 

,,         form,  composite  vessels,  154 


Fairing  by  contraction,  10 

,,        double  bottom,  41,  130 

,,        double   bottom,   battle  ship, 

137 
,,        up  belt  armour,  123 


Fairing  up  body  plan,  7 

,,  conical  gun  gallery,  142 

,,  end  gun  gallery,  145 

,,  floors,  38 

,,  frames  by  diagonal,  20 

,,  half  breadth,  8 

,,  midship  gun  gallery,  141 

,,  on  loft  floor,  7 

,,  protective  deck,  115 

,,  semi -egg  formed    gallery, 

144 
,,  shell  plating  edges,  47,  48 

,,  stern,  18 

,,  turtle  back,  87 

Fair  line,  9 

Fairness  in  sheer  draught,  9 
Fall  in  of  bilge,  5 
Figure  head  lacing  piece,  108 
,,  ,,    moulds,  108 

,,       step,  107 
Final  test  of  fairness,  10 
Finding  at  ship  moulded  depth,  106 
,,        heel     of     frames,      composite 
vessels,   154 
Finish  of  after  end,  16 

,,         belt  armour  ends,  123 
,,         planking,  sheathed  ship,  160 
Flam,  6 

Flat  plate  keel  mould    79 
Floors  at  extreme  ends,  38 
,,       in  double  bottom,  44 
,,       on  scrieve  board,  58 
,,       turned  up,  37 
Forecastle  head,  108 
Forefoot,  6 

Form  of  bell-mouth  cargo  hatches,   102 
common  harpin,  69 
forward  cants  in  sheer,  27 
iron  deck-house,  100 
lines  in  sheer  draught,  2 
ordinary  cargo  hatches,  101 
rabbet,  keel  piece,  157,  164 
ribband  line,  67 
sheer  harpin,  70 
stern  cants  in  sheer,  32 
stern  harpin,  72 
Forward  cant  frames,  27 


1(58 


INDEX. 


Forward  gun  galleries,  144 
Frame  bevels,  62,  139 

,,        application,  63 
,,        checked,  63 
,,        inner  bottom,  139 
bossed  aft,  12,  14 

,,        forward,  ram,  129 
,,        sheathed  ships,  163 
Frame  bevel  tester,  63 
Frames  canted  in  fore  body,  27 

,,         change,  6 
Framing  behind  side  armour,  119 
Freeboard  screw  steamer,  104 
,,  sailing  ship,  105 


General  description  of  box-framing, 
121 

General  description  of  barbette  struc- 
ture, 124 
General  terms  used,  3 
Gun  galleries,  141 


Half  Breadth  fairing-up,  8 

,,  plan  explained,  2 

Handy  bevelling  machine,  64 
Harpin,  bevelling  board,  70 
Harpins,  67 

Hatches  for  shipping  cargo,  101,  102 
Hawse  pipes,  102 
Head  of  forecastle,  108 
Heel    of    frames,    composite    vessels, 

154 
Hollow      section      stems     and     stern 

posts,  160 
How  lines  appear,  sheer-draught,  2 
,,     scrieve  board  is  prepared,  54 
,,     to  house  planking,  etc.,  sheathed 

vessels,  160 
. ,     to  lift  deck  sheer  side,  56 
.,     to  obtain  mast  lines,  91 
,,  ,,         round  poop  lines,  85 

,,  ,,        turtle  back  lines,  87 


Information  on  scrieve  board,  54 

Inner  bottom,  battle  ship,  137 
,,  cruiser,  130 

,,  expansion,  42,  132,  139 

,,  frame  bevels,  139 

,,  longitudinal  expansion, 

133,  135 
,,  longitudinals,   132 

,,  ribbands,  68 

Iron  deck  house,  100 

Iron  and  steel  masts,  91 


Keelsons  on  scrieve  board,  58 

,,  moulds,  83 

Keel  plate  mould,  79 
,,     rabbet,  composite  vessel,  157 
,,         ,,         sheathed  vessel,  164 
,,     scrieve  boards,  81 
Keels  on  bilge,  128 
Knees  for  beams,  88 

,,       cants,  scrieve  board,  58 
,,       tank  side,  scrieve  board,  44 
Knuckle  cut  by  diagonal,  20 


Lacing= piece  figure  head,  108 
Laying-off  beam  camber,  34 
,,         on  diagonals,  9,  55 
,,         on  loft  floor,  6 
,,         ribbands,  67 
Length  between  perpendiculars,  3 
,,        by  classification,  6 
,,        over  all,  3 
Level  line  ending,  composite  ship,  156 
Lifting  beams,  59 

,,      bevels  of  cants,  33 
,,  ,,  frames,  62 

Line  for  base,  7,  159 
„     off  draft  marks,  108,  152 
,,     of  sheer,  20 
Lines  composing  sheer  draught,  2 
,,      for  decks,  scrieve  board,  56 
,,      for  fairing-up,  8 


INDEX. 


160 


Lining  oft"  model,  46 

,,  shell  on  model,  46 

Longitudinals  of  inner  bottom,  42,  130 
Lowest  point  of  sheer,  23 


Machine  bevelling,  65 

,,  for  frame  bevel  testing,  63 

Margin  plate  expansion,  43 
Marking  oft'  freeboard,  104 

,,  hawse  pipes,  102 

Mast  doubling,  92 
,,      expansion,  91 
,,      form,  91 
,,      tube  expansion,  92 
Mclntyre  ballast  tank,  44 
Method  of  attaching   struts,   sheathed 
ships,  162 
,,      fastening,    sheathed    ships, 

160 
,,      finding  oval  form,  113 
,,  ,,      sheer  line,  20,  35 

,,      housing     planking,      etc , 

sheathed  ships,   160 
,,      laying-off  at  Swan   & 

Hunter's,  25 
, ,  , ,  beam  camber,  34 

,,  ,,  cants,  27,  32 

,,  ,,  stringer  plate,  88 

Middle     line     of     rabbet,      composite 

vessels,  155,  156 
Midship  gun  gallery,  141,  142 

,,        section,  3 
Miscellaneous,  96. 
Mocking-up  system  expansion,  135 
Mode  of  laying-off,  6 

,,        plating  protective  deck,  117 
Model  of  protective  deck,  118 
More  correct  protective    deck   expan- 
sion, 117 
Moulded  beam,  3 
,,         depth,  5 
,,         depth  at  ship,  106 
,,         form,  composite  vessels,  154 
Moulds  for  barbette  armour,  124 
,,  beams,  34,  59,  149 

,,  belt  armour,  124 


Moulds  for  boat  beams,  84 
,,  boat  davits,  151 

,,  cant  frames,  33 

,,  carver,  108 

,,  centre  through  plate  keel- 

son, 83 
,,  flat  plate  keel,  79 

,,  pilot  bridge,  151 

stem,  74,  148,  160 
,,  stern  frame,  77,  147,  160 

,,  stern  struts,  77,  149,  162 

,,  stern  tubes,  7S,  148,  162 

,,     necessary,  merchant  vessels,  74 
,,  ,,  war  vessels,  147 


Necessary  moulds,  74,  147 


Obtaining      true      form      of     shell 

plating,  49 
Obtaining  barbette  armour,  126 
,,  conical  gun  gallery,  142 

,,  double  bottom,  battle  ship, 

137 
,,  double  bottom,  cruiser,  130 

,,  double    bottom,    merchant 

ship,   41 
,,  end  gun  gallery,  145 

,,  form,  rudder  trunk,  96 

,,  ,,       shaft  tunnel,  103 

,,  midship  gun  gallery,  141 

,,  protective  deck  form,  114 

>,  ,,        expansion,  115 

,,  semi       egg  -  shaped      gun 

gallery,   144 
,,  shell  expansion,  48 

,,  shell  sight  edges,  45,  127 

,,  tank  knees,  44 

,,  turtle  back  lines,  87 

Ordinary  cargo  hatches,  101 
Ordering  shell  plating,  50 
Outer  bottom  area,  48 

,,  ,,        edges,  battle  ship,  127 

,,  ,,  ,,        cruiser,  128 

,,  ,,  ,,        merchant  ship, -J  5 

Oval  form,  113 

13 


170 


INDEX. 


Particulars  to  lay  ship  down,  3 

Pilot  bridge,  151 

Placing  shell  plating  edges  on  model, 

46 
Planking    finish    on    stem,     sheathed 
ships,  160 
,,  finish    on    stern,    sheathed 

ships,  160 
,,  thickness,  sheathed  ships,  160 

Plate  edges  of  decks,  36 

,,     keel,  79 
Plating  inner  bottom,  42,  130 
,,       of  masts,  91 
,,       outer  bottom,  45,  127 
,,       protective  deck,  117 
Poop  round  expansion,  86 
,,  form,  85 

,,  plating,  85 

Preparation  of  scrieve  board,  54 
Principal  moulds,  merchant  ships,  74 

,,  war  ships,  147 

Profile  plan  explained,  2 
Projection  in  body,  forward  cants,  29 
,,         in  sheer,  bilge  diagonal,  8 
,,         in  sheer,  forward  cants,  27 
,,         in  sheer,  stern  cants,  32 
Protective  deck,  battle  ship,  121 
,,  beams,  118 

,,  correct  expansion,  117 

,,  cruiser,  114 

,,  fairing,  115 


Rabbet  keel  piece,  composite  vessel, 
157 

Rabbet  keel  piece,  sheathed  vessel,  164 

Raised  keel,  10 

Ham,  bossed  frames,  129 

Ready  method  of  finding  sheer  line,  24 

Redoubt,  126 

Revolving  turret,  126 

Ribbands,  inner  bottom,  68 
,,  form,  67,  68 

,,  scrieve  board,  58,  67 

,,  termination  aft,  68 

,,  ,,  forward,  67 

Rise  of  bottom,  5 


Round  poop,  85 

,,     up  of  beams,  6 
Rudder  trunk,  96 


Sailing:  ship's  freeboard,  105 
Screw  steamer's  freeboard,  104 
Scrieve  board  description,  54 
,,  information,  54 

,,  keelsons,  58 

,,  preparation,  54 

Scrieve  boards  for  keel,  81 
Scrieving  in  floors,  58 

,,  frames,  55 

Seams  of  protective  deck  plating,  118 
Semi  egg-shaped  gun  gallery,  144 
Setting  off  draught  marks,  108.  152 
Shaft  brackets,  77,  149,  162 

,,     tunnel,  103 
Sheathed  ships,  160 

,,  bossed  frames,  163 

Sheer  diagram  construction,  22 
,,      draught  explained,  1 
,,      harpin  expansion,  71 
,,      line  approximately,  20 
,,      line  under  freeboard  tables,  25 
,,      of  deck  at  side,  20,  35 
Shelf  armour,  battle  ship,  123 
Shell  plating  edges,  45,  127 
,,  ,,  model,  46 

, ,  , ,         scrieve  board,  48, 57 

,,  expansion,  48,  49 

Side  armour,  battle  ship,  119 
Sighting  the  keel,  110 
Sny,  45 
Solid  stems  and  stern  posts,  sheathed 

ships,  160 
Sponsons,  141 
Stem  clipper  type,  107 

,,     finish  of  planking,  etc.,  160 
,,     mould,  merchant  ship,  74 
,,  ,,       sheathed  vessel,  160 

,,  ,,      war  vessel,  148 

,,     termination  for  ribbands,  67 
Stems  and  stern  posts,  hollow  section, 

160 
Step  for  figure  head,  107 


INDEX. 


171 


Stern  cant  frames,  32 
,,     faii'iiig-up,  18 
,,     finish  of  planking,  162 
,,  ,,        ribbands,  68 

,,     frame,  merchant  vessel,  77 
,,         ,,        sheathed  vessel,  160 
,,         ,,        war  vessel,  147 
,,     plating  expansion,  51 
,,  ,,  check,  51 

,,     tubes,  merchant  vessel,  78 
,,         ,,       sheathed  vessel,  162 
,,         ,,       war  vessel,  148 

Stringer  plate  expansion,  88 

Structure  of  barbette,  124 

Struts,  merchant  vessel,  77 
,,  sheathed  vessel,  162 
,,       war  vessel,  149 

Surface  of  deck,  expanded,  35 

Swan   and   Hunter's    method,    laying 
off,  25 

Swan's  conical  tank,  44 

System    of    planking,   etc.,    sheathed 
vessels,  160 


Taking  off  planking,    etc.,   sheathed 

vessel,  164 
Tank  knees,  44 
Taper  deck  stringer  plate,  35 
Terms  used,  3 
Test  of  fairness,  10 
The  best  line  for  fairing-up,  8 
,,    common  harpin,  69 
,,    sheer  harpin,  70 
,,    stern  harpin,  72 
Thickness  of  planking  and  shell  plating, 

sheathed  vessel,  160 
To  draw  in  deck  side,  35 
,,  end  level  line  in  half  breadth,  com- 
posite vessel,  156 
,,  fair  frames  on  diagonals,  20 
,,  find  accurately,  bearding  line,  com- 
posite vessel,  157 


To  find  accui'ately,  line  of  rabbet,  com- 
posite vessel,  156 
find  approximately,  bearding  line, 

composite  vessel,  156 
find    heel     of     frames,     composite 

vessel,  154 
find   middle   line   of   rabbet,   com- 
posite vessel,  155 
obtain   and   line   off  draft   marks, 

108,  152 
obtain  form,  curved  floors,  37 

,,  inner    bottom,    battle 

ship,  137 
,,  inner  bottom,  cruiser, 

130 
, ,  mercantile    double 

bottom,  41 
,,  of  oval,  113 

,,  protective  deck,  114 

terminate  frame  in  body,  composite 
vessel,  156 
Transferring  frame  bevels,  63 

,,        shell  sight  edges  to  boards, 57 
True  form ,  cants,  in  sheer  draught,  27, 32 
lines,  ,,  2 

,,  of  common  harpin,  69 

Tubes  for  shaft,  78,  148,  162 
Tuck  plate,  16 
Tumble  home,  5 

,,  ,,       stern  expansion,  53 

Tunnel  for  shaft,  103 
Turned  up  floors,  37 

,,  ,,  diminishing  line,  37 

Turn  of  bilge,  6 
Turret,  revolving,  126 
Turtle  back,  87 
Twin  screw  bossing,  12 

,,  covered  in  shaft,  12 


Use  of  diagonals,  9 

War  vessels,  114 
Working  base  line,  7,  159 


SOUTH     KENSINGTON     QUESTIONS 


IN 


NAVAL    ARCHITECTURE. 


ELEMENTARY    STAGE,    1867    to    1897. 
Price,  Is.,  nett.  By  Post,  Is.  <Ud. 


ADVANCED    STAGE,    1878   to    1897. 
Price,  Is.  6d.,  nett.  By  Post,  Is.  Bid. 


HONOURS    STAGE,    1878   to    1897. 
Price,  2s.  6d.,  nett.  By  Post,  2s.  6id. 


These  Question  Books  have  been  found  of  great  value  to  Students  sitting  at 
South  Kensington  and  Board  of  Trade  (Surveyors')  Examinations. 


NAVAL    ARCHITECTS'    AND    ENGINEERS' 
DATA    BOOK. 

Arranged   for  Compiling   Information  of  Vessels. 

The  book  is  used  by  a  number  of  Shipbuilders  and  others. 
Price,  3s.  6d.,  nett.  By  Post,  3s.  &1&. 

WATSON'S    DOUBLE    SLIDING    RULE, 

For  Calculating  Displacement,  Tonnage,  Speed, 
and  Indicated  Horse-power. 

This  rule  is  extremely  easy  to  understand  and  work.     It  is  so  small  in  size 
that  it  may  be  carried  in  an  ordinary  pocket  without  inconvenience. 

Made  of  Boxwood,  price  12s.  6d.,  nett. 


Compiled  and  Sold  by 

THOMAS    H.    WATSON, 
NAVAL    ARCHITECT    AND    SHIP    SURVEYOR, 

io,  Neville  Street,  Newcastle=on=Tyne. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
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